Twelve earthen field fortifications on Fort Eustis are associated with the 1861-1862 Peninsula Campaign of the American Civil War and formed part of the Warwick-Yorktown line developed by Confederate Major General John B. Magruder to prevent or at least slow the U.S. Army's advance from Fort Monroe on the James-York peninsula toward the Confederate capitol at Richmond. Built over the winter of 1861-1862, mainly with enslaved labor, these works closely followed the designs in Colonel Dennis Hart Mahan's Treatise on Field Fortifications. The largest fortification on Mulberry Island, now called Fort Crafford, was an eight-acre bastioned covering work that protected the Mulberry Island Point Battery, which was intended to work with Fort Huger across the James River to prevent the U.S. Navy from using the river to assault Richmond. In May of 1862, the Confederates retreated toward Richmond and the war moved on to other parts of Virginia.
