During the Civil War 180,000 African Americans comprising 170 regiments served in the Union Army and 29,511 served in the Union Navy. Army regiments composed of black soldiers were known as the United States Colored Troops (USCT). Many of the men who served as USCT were slaves prior to volunteering for the Union Army. In St. Mary's County during the 1800s there were more than 6,500 slaves and over 700 were recruited as USCT.

This monument honors the United States Colored Troops and all Union soldiers and sailors from St. Mary’s County who fought during the Civil War. It pays special tribute to USCT soldiers, Pvt. William H. Barnes and Sgt. James H. Harris who earned the Medal of Honor for gallantry at the Battle of New Market Heights, Va., in September 1864. Joseph B. Hayden of St. Mary’s County, a white Civil War sailor in the United States Navy, earned the Medal of Honor for his bravery on board the U.S.S. Ticonderoga, during attacks on Fort Fisher, 13 to 15 January 1865.