After Confederate forces abandoned Fort Heiman in February 1862, Federal troops occupied it until March 6, 1863. The fort was strengthened and became a major supply depot for Union troops and gunboats. A new fortification, Federal Fort, was also built about half a mile behind the Confederate fort. Much of it still exists, and it became the center of an extensive encampment and road complex. During 1862-63, the new Federal Fort and old Fort Heiman helped protect and maintain the vital supply line of the Tennessee River. Together with Forts Henry and Donelson, they also offered havens for growing numbers of refugees, most of whom were slaves seeking safety within Union lines. Before permanently abandoning Fort Heiman on March 6, 1863, Union troops destroyed the part of the fort's earthworks along the river but left largely intact the breastworks along the crest of the bluffs and an upper battery or redoubt. Remnants of these breastworks and what may have been a powder magazine remain on the site.