Ohio Slack Water Dams, Lock & Dam No. 4, East bank of Ohio River at mile point 18.6, along State Route 65, Ambridge, Beaver County, PA
Significance: Ohio Slack Water Dams, Lock and Dam No. 4, HAER No. PA-227-A was part of the fifty-two slackwater locks and dams constructed by the U.S. Army Corps of Engineers on the Ohio River, between 1877-1917. The Lock and Dam complexes on the Ohio River insured year-round depths of 9.0 feet from the Mississippi River to Pittsburgh, Pennsylvania.
Survey number: HAER PA-227-A
Building/structure dates: 1898-1908 Initial Construction
Building/structure dates: 1936 Subsequent Work
Building/structure dates: 1992 Subsequent Work