Fort Jackson, designed to hold the middle of Camp Nelson's northern line, was 280 feet deep and 300 feet wide, with breastworks ten feet high. It was a lunette, a four-sided unenclosed fort, and one of three forts on the northern line that mounted artillery. Although it had 13 gun platforms, it never mounted more than seven guns: six 12-pounder Napoleon cannons and one 30-pounder Parrott, and it also had a powder magazine. Its inside wall was braced, or revetted, with wooden planks, and bundles of sticks called facines braced the inside of the embrasures. Because bedrock made it impossible to dig the ditch in front of the fort as deep as regulations specified, engineers made the ditch wider and placed in it a barrier of felled cedar and thorn-locust trees called an abatis that was nearly impenetrable. The fort was named for General James S. Jackson, a Kentuckian who gave up his seat in the U.S. House of Representatives to raise the 3rd Kentucky Cavalry (U.S.). Born September 27, 1823, in Fayette County, he attended Centre College in Danville and studied law at Transylvania University in Lexington. After serving in the Mexican War, he returned to his law practice and entered politics, then in 1861 ran as a Unionist and won a seat in Congress. When the war began, he resigned to serve in the Union Army, earned the rank of brigadier general of volunteers in July 1862, and died at the Battle of Perryville, Kentucky, on October 8, 1862, while trying to rally his men. He was buried in Riverside Cemetery in Hopkinsville, Kentucky. On September 15, 1864, Chief Engineer John R. Gilliss wrote that the fort's comparatively low position allowed Forts Nelson and Taylor to fire over it safely while its guns protected the ground to the front and its flanking guns enfiladed the abatis line from Fort Nelson to Battery Pope.