The Seven Foot Knoll Light was built in 1855 and is the oldest screw-pile lighthouse in Maryland. It was located atop Seven Foot Knoll in the Chesapeake Bay until it was replaced by a modern navigational aid and relocated to Baltimore's Inner Harbor as a museum exhibit.

A screw-pile lighthouse is a lighthouse which stands on piles that are screwed into sandy or muddy sea or river bottoms. The first screw-pile lighthouse to begin construction was built by the blind Irish engineer Alexander Mitchell. Construction began in 1838 at the mouth of the Thames and was known as the Maplin Sands lighthouse, and first lit in 1841. However, though its construction began later, the Wyre Light in Fleetwood, Lancashire, was the first to be lit.