As Union military occupation spread over Middle Tennessee, Federal commanders needed a supply depot on the Tennessee River, and by 1863 they agreed that a year-round navigable depot would provide Union armies in the West with vital supplies. To connect it with Nashville, Gen. William Rosecrans ordered in October 1863 that the Nashville and Northwestern Railroad, which ended at Kingston Springs, be extended to the Tennessee River. The 1st Michigan Engineer Regiment designed the line, and 5,000 conscripted African American laborers from surrounding counties built it. By May 1864, the 90-acre depot included a sawmill, docks, wharves, offices, warehouses, horse corrals, and quarters for 2,500 soldiers, and Union soldiers constructed a fort that U.S. Colored Troops manned to protect the depot. On May 10, Tennessee military governor Andrew Johnson, later the 17th U.S. President, rode the first train 78 miles from Nashville to the new depot and, according to witnesses, named the place after himself, after which the depot and town were called Johnsonville. On November 4, 1864, Confederate Gen. Nathan Bedford Forrest attacked Johnsonville from the western bank of the Tennessee River. When Union commander Col. Charles R. Thompson ordered all vessels burned to prevent their capture, the fire also engulfed most of the buildings there, and losses were estimated in the millions of dollars. Early in 1865, the Union army abandoned the depot except for a small U.S. Colored Troops detachment. After the war, Johnsonville flourished as a railroad town. In 1867, the Tennessee River was bridged to the western shore, allowing trains to run continuously between Nashville and Memphis. Johnsonville ceased to exist 80 years later, when in the mid-1940s the Tennessee Valley Authority dammed the Tennessee River and formed Kentucky Lake. The fort and defensive lines are listed in the National Register of Historic Places and comprise the Johnsonville State Historic Park.