The Seven-Foot Knoll Lighthouse was built as part of an effort to revitalize the nation’s system of navigational aids, under the leadership of a new Lighthouse Board. Plans to build a lighthouse at the  mouth of the Patapsco River began in 1851, to mark the  entrance to the Chesapeake Bay.

The Seven Foot Knoll Lighthouse is a screwpile lighthouse, meaning that it is supported on iron columns that would have been drilled into the rocky shoal of its original location. The screwpile technology eliminated the need for underwater caissons and heavy masonry foundations, and is based on the principle of a fixed structural support system of piles driven into the river bottom. Completed in 1855, the lighthouse exterior is constructed of iron, and was fabricated by the Baltimore foundry Murray and Hazelhurst. Lighthouse keepers lived on site and maintained Seven Foot Knoll Lighthouse until 1948, when the beacon was automated. In 1988, the lighthouse was moved from its original location to Pier 5 in the harbor, to avoid demolition. The lighthouse is currently maintained by Historic Ships in Baltimore, which also operates four other ship museums in the inner harbor.