Upper Mississippi River 9-Foot Channel Project, Lock & Dam 27, Granite City, Madison County, IL

Significance: ...Lock and Dam No. 27 constitute additions to the original Upper Mississippi Nine-Foot Channel Project, constructed after World War II. Lock No. 27, located on the Chain of Rocks Canal, provided the last link in the nine-foot channel, facilitating safe passage around the dangerous Chain of Rocks Reach. The design and construction of the locks incorporated various engineering and technological lessons and advances learned during the completion of the earlier elements of the project during the 1930s. Dam No. 27, constructed in the early 1960s, provides additional depth of water in the pool, extending upstream to Lock and Dam No. 26, facilitating more efficient operation of that installation. Dam No. 27 is the first dam ever constructed completed across the Mississippi River. It is emblematic of the continued efforts to refine and improve the nine-foot channel.
Survey number: HAER IL-33
Building/structure dates: 1947 Initial Construction
Building/structure dates: 1964 Subsequent Work