Pleasant Valley Roller Mill, Gruber Road, Bernville, Berks County, PA
Significance: This handsome masonry building, minus its 1946 frame addition, is highly typical of canal-related mils in the region. Although it clearly reflects its proximity to the Union Canal, it occupied th... More
McPherson Bridge, Spanning Candies Creek at County Road A165, Eureka, ...
Significance: Most features of the bridge are representative of truss bridges. The vertical members are paired angles with double lacing. The counters and diagonals are I-bars or tie-rods. The top chords and en... More
Murtaugh Bridge, Murtaugh, Twin Falls County, ID
Significance: This Pratt truss bridge was constructed in the early years of the twentieth century to provide north-south access across the Snake River. The need for River crossings increased as development of ... More
Pawtucket Canal, Lower Locks, Lowell, Middlesex County, MA
Significance: The Lower Locks are comprised of two navigation locks and a dam, with a head of 17 feet. They were some of the earliest locks in the Lowell Canal System, originally constructed in the first phase... More
Pawtucket Canal, Lower Locks, Lowell, Middlesex County, MA
Significance: The Lower Locks are comprised of two navigation locks and a dam, with a head of 17 feet. They were some of the earliest locks in the Lowell Canal System, originally constructed in the first phase... More
North Fork Bridge, Spanning North Fork of Licking River, Milford, Brac...
Significance: The North Fork Bridge is the oldest dated Pratt through truss bridge in Kentucky, and one of two built by the Smith Bridge Company in the state of Kentucky. Survey number: HAER KY-2 Building/str... More
North Fork Bridge, Spanning North Fork of Licking River, Milford, Brac...
Significance: The North Fork Bridge is the oldest dated Pratt through truss bridge in Kentucky, and one of two built by the Smith Bridge Company in the state of Kentucky. Survey number: HAER KY-2 Building/str... More
North Fork Bridge, Spanning North Fork of Licking River, Milford, Brac...
Significance: The North Fork Bridge is the oldest dated Pratt through truss bridge in Kentucky, and one of two built by the Smith Bridge Company in the state of Kentucky. Survey number: HAER KY-2 Building/str... More
Northern Canal, Great River Wall, Lowell, Middlesex County, MA
Significance: The Great River Wall is a massive retaining wall which separates the upper half of the Northern Canal from the Merrimack River. Survey number: HAER MA-8-B Building/structure dates: 1847 Initial ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Bridge No. 28, Spanning Flatt River at State Route 1004, Durham, Durha...
Significance: The bridge consists of three identical spans, each 70 feet long and divided into five panels. Its members are built of channels and angles joined by stay pieces and lace bars. The heavy construc... More
E. & T. Fairbanks & Company Factory, Sleepers River, Saint Johnsbury, ...
Significance: This factory manufactured the famous platform scales invented by Thaddeus Fairbanks in 1830. The factory complex, which was comprised of 40 buildings containing 23 acres of floor space, has been ... More
Mott Rainbow Arch Bridge, Spanning Cannonball River, Mott, Hettinger C...
Significance: This structure is one of only two reinforced concrete bridges known to exist in North Dakota in 1980. It is a good representative of the Marsh Rainbow Arch Bridge design. Survey number: HAER ND-... More
Western Canal, Pawtucket & Merrimack Canals vicinity, Lowell, Middlese...
Significance: The Western Canal was the only power canal in Lowell to be built on two levels, though the Pawtucket Canal also had an upper and a lower level. Construction on two levels meant that the same wate... More
Boston & Worcester Railroad, Bogastow Brook Viaduct, Spanning Bogastow...
Significance: The Bogastow Brook Viaduct is a 260 foot long, 8 arch stone viaduct. It carries the tracks of the Boston & Worcester Railroad across Bogastow Brook, and also spanned the tailrace of the Holliston... More
Northern Canal, Pawtucket & Ford Streets vicinity, Lowell, Middlesex C...
Significance: The Northern Canal was constructed to bring more water into the canal system in order that the demands for power made by increasingly large mills could be met. The Northern Canal supplemented the... More
American Woolen Company, East Canal Street, Winooski, Chittenden Count...
Significance: The Champlain Mill is a good representative example of late nineteenth century New England mill architecture. The structure is a four-story brick building, with slightly arched windows and corbel... More
Anaconda Historic District, Ancient Order of Hibernians Hall, 321-323 ...
Significance: This building was the headquarters for the local chapter of the Ancient Order of Hibernians, an Irish fraternal organization first established in Anaconda in 1885. The A.O.H. auxiliary was offici... More
Anaconda Historic District, Ancient Order of Hibernians Hall, 321-323 ...
Significance: This building was the headquarters for the local chapter of the Ancient Order of Hibernians, an Irish fraternal organization first established in Anaconda in 1885. The A.O.H. auxiliary was offici... More
Louisville Water Company Pumping Stations, Zorn Avenue & River Road, L...
Significance: Theodore R. Scowden, chief engineer for the Louisville Water Company, designed Pumping Station No. 1 in the Classical Revival style in 1856. The complex included an engine room and boiler house i... More
Louisville Water Company Pumping Stations, Zorn Avenue & River Road, L...
Significance: Theodore R. Scowden, chief engineer for the Louisville Water Company, designed Pumping Station No. 1 in the Classical Revival style in 1856. The complex included an engine room and boiler house i... More
Pawtucket Canal, Guard Locks, Lowell, Middlesex County, MA
Significance: The Guard Locks were the first set of locks constructed in the Lowell System which are still in existence. They have, however, been altered and added to since first put into use. The Guard Locks... More
Pawtucket Canal, Guard Locks, Lowell, Middlesex County, MA
Significance: The Guard Locks were the first set of locks constructed in the Lowell System which are still in existence. They have, however, been altered and added to since first put into use. The Guard Locks... More
Pawtucket Canal, Guard Locks, Lowell, Middlesex County, MA
Significance: The Guard Locks were the first set of locks constructed in the Lowell System which are still in existence. They have, however, been altered and added to since first put into use. The Guard Locks... More
Pawtucket Canal, Guard Locks, Lowell, Middlesex County, MA
Significance: The Guard Locks were the first set of locks constructed in the Lowell System which are still in existence. They have, however, been altered and added to since first put into use. The Guard Locks... More
Union Canal Locks, Bernville, Berks County, PA
Significance: The ruins of these locks document 19th-century canal technology, and illustrate the importance of water transportation in the first half of the century. Although the Union Canal failed to become ... More
Union Canal Locks, Bernville, Berks County, PA
Significance: The ruins of these locks document 19th-century canal technology, and illustrate the importance of water transportation in the first half of the century. Although the Union Canal failed to become ... More
Pawtucket Canal, Swamp Locks, Pawtucket & Merrimack Canals, Lowell, Mi...
Significance: The Swamp Locks complex consists of a flight of two navigation locks with a dam at the west end of the upper lock. The original locks opened in 1797, and were rebuilt in 1822-1823 when this confi... More
Continental Gin Company, Prattville, Autauga County, AL
Significance: The site was acquired by Daniel Pratt in 1838, and he soon established grist and lumber and shingle mills there. By 1844, he had opened a cotton gin plant, the products of which were in great dem... More
Continental Gin Company, Prattville, Autauga County, AL
Significance: The site was acquired by Daniel Pratt in 1838, and he soon established grist and lumber and shingle mills there. By 1844, he had opened a cotton gin plant, the products of which were in great dem... More
Continental Gin Company, Prattville, Autauga County, AL
Significance: The site was acquired by Daniel Pratt in 1838, and he soon established grist and lumber and shingle mills there. By 1844, he had opened a cotton gin plant, the products of which were in great dem... More
Continental Gin Company, Prattville, Autauga County, AL
Significance: The site was acquired by Daniel Pratt in 1838, and he soon established grist and lumber and shingle mills there. By 1844, he had opened a cotton gin plant, the products of which were in great dem... More
Continental Gin Company, Prattville, Autauga County, AL
Significance: The site was acquired by Daniel Pratt in 1838, and he soon established grist and lumber and shingle mills there. By 1844, he had opened a cotton gin plant, the products of which were in great dem... More
Continental Gin Company, Prattville, Autauga County, AL
Significance: The site was acquired by Daniel Pratt in 1838, and he soon established grist and lumber and shingle mills there. By 1844, he had opened a cotton gin plant, the products of which were in great dem... More
Anaconda Historic District, 319 East Commercial Avenue, Anaconda, Deer...
Significance: This one-story brick building has a cast metal facade with wooden inlay and a pressed metal cornice at the parapet wall. The structure measures 25' x 80' and was built by Joseph Petritz in 1890. ... More
West End Street Railway, Cleveland Circle Car House, Chestnut Hill Ave...
Significance: The Cleveland Circle Car House was a depot for the West End Street Railway, the first electric streetcar line in Boston, established in 1889. In the 1890s, this became the largest electric street... More
Anaconda Historic District, Park & Commercial Streets, Main Street vic...
Significance: Anaconda was established in 1885 by Marcus Daly on Warm Springs Creek, as the site of the smelter for the Amalgamated Copper Mining Company. The site was selected for its proximity to the mines a... More
Starnes Bridge, Spanning Eagle Creek, Holbrook, Grant County, KY
Significance: The Starnes Bridge is a rare surviving example of bridge technology representing the pin-connected Pennsylvania truss elements. Survey number: HAER KY-3 Building/structure dates: 1890 Initial Co... More
Anaconda Historic District, Mahie Block, 124 East Commercial Avenue, A...
Significance: This two-story brick structure has an art deco era steel facade over plate glass storefront windows, and stucco side and rear exterior walls. The building today is a dramatically altered version ... More
Anaconda Reduction Department, Southeast side of Warm Springs Valley, ...
Significance: The Foundry Department of the Anaconda Reduction Department was organized as an independent venture in the late 1880s. Originally known as the Anaconda Hardware Company - dealers in stoves, iron, ... More
Moody Street Feeder, Gatehouse, Moody Street Feeder & Merrimack Canal,...
Significance: The Moody Street Feeder Gatehouse contains manually controlled equipment for operating the sluice gates which were used to control the flow of water through the Moody Street Feeder. Survey number... More
Moody Street Feeder, Gatehouse, Moody Street Feeder & Merrimack Canal,...
Significance: The Moody Street Feeder Gatehouse contains manually controlled equipment for operating the sluice gates which were used to control the flow of water through the Moody Street Feeder. Survey number... More
George Washington Bridge, Spanning Hudson River between Manhattan & Fo...
Significance: At the time of its construction, the George Washington Bridge was the longest span suspension bridge in the world. Survey number: HAER NY-129
George Washington Bridge, Spanning Hudson River between Manhattan & Fo...
Significance: At the time of its construction, the George Washington Bridge was the longest span suspension bridge in the world. Survey number: HAER NY-129
George Washington Bridge, Spanning Hudson River between Manhattan & Fo...
Significance: At the time of its construction, the George Washington Bridge was the longest span suspension bridge in the world. Survey number: HAER NY-129
George Washington Bridge, Spanning Hudson River between Manhattan & Fo...
Significance: At the time of its construction, the George Washington Bridge was the longest span suspension bridge in the world. Survey number: HAER NY-129
Manhattan Bridge, Spanning East River at Flatbush Avenue, between New ...
Significance: This single span suspension bridge contains one of the longest suspension spans in the U.S., and had the largest carrying capacity in the country when it was built. It is unusual in that it was d... More
Manhattan Bridge, Spanning East River at Flatbush Avenue, between New ...
Significance: This single span suspension bridge contains one of the longest suspension spans in the U.S., and had the largest carrying capacity in the country when it was built. It is unusual in that it was d... More
Mountain Home Veterans Administration Medical Center, Johnson City, W...
For additional documentation see HABS TN-254. Significance: It was established in 1901 as the Mountain Branch of the National Home for Disabled Volunteer Soldiers. The establishment of the Mountain Branch was b... More
Mountain Home Veterans Administration Medical Center, Johnson City, W...
For additional documentation see HABS TN-254. Significance: It was established in 1901 as the Mountain Branch of the National Home for Disabled Volunteer Soldiers. The establishment of the Mountain Branch was b... More
Western Canal, Hickey Hall Dam, Lowell, Middlesex County, MA
Significance: The Hickey Hall Dam was built to ensure the water level in the upper level of the Western Canal was sufficiently high to provide power to the Suffolk and Tremont Mills prior to construction of the... More
Williamsburg Bridge, Spanning East River at South Sixth Street between...
Significance: The Williamsburg Bridge is the longest span suspension bridge over the East River, its span exceeding that of the Brooklyn Bridge by 4.5 feet. Survey number: HAER NY-128 Building/structure dates... More
Lowell Canal System, Merrimack & Concord Rivers, Lowell, Middlesex Cou...
Significance: The City of Lowell is generally considered to be the birthplace of large-scale manufacturing in the U.S. Begun as a transportation canal, the Lowell Canal System evolved, during the 19th century,... More
Chow Chow Suspension Bridge, Spanning Quinault River, Taholah, Grays H...
Significance: The Chow Chow Suspension Bridge was constructed by Native Americans living on the Quinault Indian Reservation about 1950. It consists of four timber king post trusses that are suspended from stee... More
Atherton Bridge, Spanning Nashua River on Bolton Road, Lancaster, Worc...
Significance: The Atherton Bridge is an example of a hybrid pony-truss that bears a similarity to the Post truss. The bridge is 72 feet long, 18 1/2 feet wide, and is comprised of eight panels. It rests on gr... More
Atherton Bridge, Spanning Nashua River on Bolton Road, Lancaster, Worc...
Significance: The Atherton Bridge is an example of a hybrid pony-truss that bears a similarity to the Post truss. The bridge is 72 feet long, 18 1/2 feet wide, and is comprised of eight panels. It rests on gr... More
Queensboro Bridge, Spanning East river & Blackwell's Island, New York,...
Significance: At the time of construction, the Queensboro Bridge contained the longest cantilever span in America. Survey number: HAER NY-19 Building/structure dates: 1909 Initial Construction
Ponakin Road Bridge, Spanning Nashua River on Ponakin Road, Lancaster,...
Significance: The single span Ponakin Road Bridge is 100 feet long and 20 feet wide, with vertical end posts. The bridge has diagonal compression members and diagonal eye-bar tension members that extend two pa... More
Ponakin Road Bridge, Spanning Nashua River on Ponakin Road, Lancaster,...
Significance: The single span Ponakin Road Bridge is 100 feet long and 20 feet wide, with vertical end posts. The bridge has diagonal compression members and diagonal eye-bar tension members that extend two pa... More
Ponakin Road Bridge, Spanning Nashua River on Ponakin Road, Lancaster,...
Significance: The single span Ponakin Road Bridge is 100 feet long and 20 feet wide, with vertical end posts. The bridge has diagonal compression members and diagonal eye-bar tension members that extend two pa... More
Ponakin Road Bridge, Spanning Nashua River on Ponakin Road, Lancaster,...
Significance: The single span Ponakin Road Bridge is 100 feet long and 20 feet wide, with vertical end posts. The bridge has diagonal compression members and diagonal eye-bar tension members that extend two pa... More
Anaconda Historic District, Washoe Theater, 305 Main Street, Anaconda,...
Significance: Designed by B. Marcus Priteca, Architect, and built by Gus Forseen, Missoula contractor, the Washoe Theater opened to the public on September 24, 1936. Both the Theater's structural architecture ... More
Pleasant Valley Roller Mill, Gruber Road, Bernville, Berks County, PA
Significance: This handsome masonry building, minus its 1946 frame addition, is highly typical of canal-related mils in the region. Although it clearly reflects its proximity to the Union Canal, it occupied th... More
Anaconda Historic District, Durston Building, Main Street & East Park ...
Significance: This stately three-story brick building was erected by J.H. Durston, prominent editor of the Anaconda Standard. The eastern annex, known as the "Baby Durston," was added in 1902. The storefronts... More
McPherson Bridge, Spanning Candies Creek at County Road A165, Eureka, ...
Significance: Most features of the bridge are representative of truss bridges. The vertical members are paired angles with double lacing. The counters and diagonals are I-bars or tie-rods. The top chords and en... More
McPherson Bridge, Spanning Candies Creek at County Road A165, Eureka, ...
Significance: Most features of the bridge are representative of truss bridges. The vertical members are paired angles with double lacing. The counters and diagonals are I-bars or tie-rods. The top chords and en... More
Pawtucket Canal, Lower Locks, Lowell, Middlesex County, MA
Significance: The Lower Locks are comprised of two navigation locks and a dam, with a head of 17 feet. They were some of the earliest locks in the Lowell Canal System, originally constructed in the first phase... More
Pawtucket Canal, Lower Locks, Lowell, Middlesex County, MA
Significance: The Lower Locks are comprised of two navigation locks and a dam, with a head of 17 feet. They were some of the earliest locks in the Lowell Canal System, originally constructed in the first phase... More
North Fork Bridge, Spanning North Fork of Licking River, Milford, Brac...
Significance: The North Fork Bridge is the oldest dated Pratt through truss bridge in Kentucky, and one of two built by the Smith Bridge Company in the state of Kentucky. Survey number: HAER KY-2 Building/str... More
Northern Canal, Great River Wall, Lowell, Middlesex County, MA
Significance: The Great River Wall is a massive retaining wall which separates the upper half of the Northern Canal from the Merrimack River. Survey number: HAER MA-8-B Building/structure dates: 1847 Initial ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Thames Tow Boat Company, Foot of Farnsworth Street, New London, New Lo...
Significance: The Thames Shipyard has been in constant use from the time of its completion in 1903 to the present (as of 1978). Originally constructed to build and repair ocean-going tugs and barges, the yard ... More
Union Station, Water Street, Montgomery, Montgomery County, AL
Significance: Montgomery's Union Station is an impressive Romanesque structure, and an excellent example of late nineteenth century commercial architecture. Its size, the ambitiousness of its design, and its o... More
Union Station, Water Street, Montgomery, Montgomery County, AL
Significance: Montgomery's Union Station is an impressive Romanesque structure, and an excellent example of late nineteenth century commercial architecture. Its size, the ambitiousness of its design, and its o... More
Union Station, Water Street, Montgomery, Montgomery County, AL
Significance: Montgomery's Union Station is an impressive Romanesque structure, and an excellent example of late nineteenth century commercial architecture. Its size, the ambitiousness of its design, and its o... More
Eastern Canal, Boott Penstock, Between Eastern & Merrimack Canals, Low...
Significance: The existing penstock is fifth in a succession of channels conveying water from the Eastern Canal to the Merrimack Canal. The first of the penstocks was probably built about 1835, at the same tim... More
E. & T. Fairbanks & Company Factory, Sleepers River, Saint Johnsbury, ...
Significance: This factory manufactured the famous platform scales invented by Thaddeus Fairbanks in 1830. The factory complex, which was comprised of 40 buildings containing 23 acres of floor space, has been ... More
Mott Rainbow Arch Bridge, Spanning Cannonball River, Mott, Hettinger C...
Significance: This structure is one of only two reinforced concrete bridges known to exist in North Dakota in 1980. It is a good representative of the Marsh Rainbow Arch Bridge design. Survey number: HAER ND-... More
Mott Rainbow Arch Bridge, Spanning Cannonball River, Mott, Hettinger C...
Significance: This structure is one of only two reinforced concrete bridges known to exist in North Dakota in 1980. It is a good representative of the Marsh Rainbow Arch Bridge design. Survey number: HAER ND-... More
Mott Rainbow Arch Bridge, Spanning Cannonball River, Mott, Hettinger C...
Significance: This structure is one of only two reinforced concrete bridges known to exist in North Dakota in 1980. It is a good representative of the Marsh Rainbow Arch Bridge design. Survey number: HAER ND-... More
Northern Canal, Pawtucket & Ford Streets vicinity, Lowell, Middlesex C...
Significance: The Northern Canal was constructed to bring more water into the canal system in order that the demands for power made by increasingly large mills could be met. The Northern Canal supplemented the... More
Northern Canal, Pawtucket & Ford Streets vicinity, Lowell, Middlesex C...
Significance: The Northern Canal was constructed to bring more water into the canal system in order that the demands for power made by increasingly large mills could be met. The Northern Canal supplemented the... More
American Woolen Company, East Canal Street, Winooski, Chittenden Count...
Significance: The Champlain Mill is a good representative example of late nineteenth century New England mill architecture. The structure is a four-story brick building, with slightly arched windows and corbel... More
American Woolen Company, East Canal Street, Winooski, Chittenden Count...
Significance: The Champlain Mill is a good representative example of late nineteenth century New England mill architecture. The structure is a four-story brick building, with slightly arched windows and corbel... More
Poughkeepsie Bridge, Spanning Hudson River, Poughkeepsie, Dutchess Cou...
Significance: Major 19th century cantilever bridge, located at an important crossing of the Hudson. Survey number: HAER NY-131 Building/structure dates: 1889 Initial Construction
Pawtucket Canal, Guard Locks, Lowell, Middlesex County, MA
Significance: The Guard Locks were the first set of locks constructed in the Lowell System which are still in existence. They have, however, been altered and added to since first put into use. The Guard Locks... More
Pawtucket Canal, Guard Locks, Lowell, Middlesex County, MA
Significance: The Guard Locks were the first set of locks constructed in the Lowell System which are still in existence. They have, however, been altered and added to since first put into use. The Guard Locks... More
Pawtucket Canal, Guard Locks, Lowell, Middlesex County, MA
Significance: The Guard Locks were the first set of locks constructed in the Lowell System which are still in existence. They have, however, been altered and added to since first put into use. The Guard Locks... More