On August 15, 1865, Colonel Kidd's column selected the site of the fort on a bluff above the Powder River near the crossing of the Bozeman Trail. Construction began the same day by the four companies of the 6th Michigan Cavalry that had recently been transferred from the Army of the Potomac in Virginia. The new post was named Fort Connor in honor of Brigadier General Patrick Edward Connor, the overall commander of the Powder River Expedition. That month, Fort Connor was the jumping-off point for the soldiers that fought at the Battle of the Tongue River on August 29, 1865 in present-day Sheridan County, Wyoming. The left, right, and center columns of the Powder River Expedition all finally rendezvoused at Fort Connor on September 25, 1865. Army units that arrived in September included companies from the 2nd Missouri Volunteer Light Artillery Regiment, 12th Missouri Volunteer Cavalry Regiment, 15th Kansas Volunteer Cavalry Regiment, and the 16th Kansas Volunteer Cavalry Regiment, along with a second detachment of the U.S. Signal Corps. Most of these men marched south to Fort Laramie in October, 1865 to be mustered out of the army, leaving the four companies of Michigan cavalry under Colonel James H. Kidd to garrison the fort.