The base covers parts of Bullitt, Hardin, and Meade Counties and extends over 109,054 acres and holds around 32,000 people daily. Fortifications were not constructed at the site until 1862, during the Civil War when Fort Duffield was founded. The area was contested by both Union and Confederate forces. After the war the site fell into disuse. the area was revived for military operations in 1917, 10,000 acres near to the village of Stithton were leased to the government and a training center was established on the site in January 1918. The new camp was named after Henry Knox, a general of artillery during the American Revolutionary War and the country's first Secretary of War. The camp was extended by the purchase of a further 40,000 acres in June, 1918 and construction proper began in July 1918. The building program was reduced following the end of the war and reduced further following cuts to the army in 1921 after the National Defense Act of 1920. The camp was greatly reduced and became a semi-permanent training center.
In 1931 a small force of the Mechanized Cavalry was assigned to Camp Knox to use it as a training site. The camp was turned into a permanent garrison in January 1932 and re-named Fort Knox, the 1st Cavalry Regiment arrived later in the month to become the 1st Cavalry Regiment (Mechanized). In 1936 the 1st was joined by the 13th to become the 7th Cavalry Brigade (Mechanized). The site quickly became the centre for mechanization tactics and doctrine. The success of the German mechanized units at the start of WW II were a major impetus to operations at the fort. A new Armored Force was established in July 1940 with its headquarters at Fort Knox with the 1st Cavalry becoming the 1st Armored Division. The Armored Force School and the Armored Force Replacement Center were also sited at Fort Knox in October, 1940. The site was expanded to cope with its new role, by 1943 there were 3,820 buildings on 106,861 acres.
In 1936 the Treasury Department began construction of the U.S. Bullion Depository adjacent to Fort Knox on land deeded from the military. The 'Gold Vault' was completed in Decmeber 1936 at a cost of $560,000 and the first gold shipments were made from January to July 1937. The majority of the country's gold reserves were gradually shipped to the site. During the war the depository also held the reserves of a number of European countries as well as the British crown jewels, the Magna Carta and key documents from American history. Gold holdings peaked in the war at 649.6 million ounces. Current holdings are around 147 million ounces in around 368,000 standard 400 ounce bars. The depository also holds monetary gold.
The Patton Museum of Cavalry and Armor was established at Fort Knox in 1949.
There is another Fort Knox in Maine, built from 1844-1869.