Built by the Maryland colony in 1756 during the French and Indian War, Fort Frederick had stone walls surrounding three large buildings. The colonists abandoned the frontier fort in 1759 after the threat of Indian raids subsided. During the Revolutionary War, it held hundreds of British prisoners. The state auctioned the fort and about 100 acres in the 1790s, and after the property changed hands several times, Nathan Williams, a free African American, bought it in 1860 and farmed the land. By then, time and scavengers had demolished the buildings. With the outbreak of the Civil War in 1861, the area around Fort Frederick again became strategically significant as the U.S. Army sought to protect the Chesapeake and Ohio Canal a quarter-mile south and the Baltimore and Ohio Railroad across the Potomac River in present-day West Virginia. The 1st Maryland Infantry (U.S.), under Colonel John Kenly, arrived in December 1861 to guard the canal and the fords and ferries between Four Locks and Cherry Run, and Company H occupied Fort Frederick. On Christmas Day 1861, the regiment skirmished nearby with Confederate raiders who tore up the railroad. Company D relieved Company H in January 1862, then crossed the river at the end of February to protect the railroad during repairs. In October 1862, a 12th Illinois Cavalry picket guarded the canal immediately south of old Fort Frederick, and other Federal forces later occupied the area.