Fort Ellis Fort Ellis was a United States Army fort established August 27 , 1867 , east of present - day Bozeman , Montana . Troops from the fort participated in many major campaigns of the Indian Wars . The fort was closed in 1886 . History . The fort was established to protect and support settlers moving into the Gallatin Valley . The post was named for Colonel Augustus van Horne Ellis who was killed in 1863 at the Battle of Gettysburg during the Civil War . Five companies of the 2nd Cavalry and infantry companies from the 7th Infantry Regiment provided the fort ' s garrison . Nearby Fort Elizabeth Meagher which was established in the spring of 1867 on Rocky Creek was abandoned when Fort Ellis was built . Fort Ellis was an important post during the prominent Indian conflicts of the 19th century as well as a base of operations for exploring the region now known as Yellowstone National Park . In January 1870 Major Eugene M . Baker led elements of the Second Cavalry against elements of the Piegan tribe , culminating in the Marias Massacre on the Marias River in Montana . In April 1876 Colonel John Gibbon departed Fort Ellis with 400 infantry and cavalry as the " Montana Column " during the summer campaign of the Great Sioux War of 1876 - 77 . Troops from Fort Ellis also participated in the Nez Perce War in 1877 . The fort provided military escorts for a number of prominent expeditions into the Yellowstone region . In 1870 , Lieutenant Gustavus C . Doane and five cavalrymen escorted Henry Washburn and eight other civilians from Helena , Montana on the Washburn - Langford - Doane Expedition . Doane would also accompany expeditions in 1871 and 1875 , as well as an ill - fated exploration of the Snake River in 1876 . Like many Frontier garrisons , the fort had an ambivalent relationship with the nearby town of Bozeman , located 3 miles to the west of the fort . On 11 December 1867 and again 14 December 1867 , soldiers of the 13th US Infantry destroyed buildings in and around the town that were found to be selling alcohol to the soldiers . Through the post ' s history , the settlers of Bozeman enjoyed the federal money brought to the city by contracts and payroll , but often acted nefariously as they competed amongst themselves for those dollars Decommissioning . Since the post was located on prime agricultural land , many settlers in Bozeman petitioned to have the post closed . Documents indicate that the post would likely have remained active for several more years but since Gen . Sherman struggled to find posts to close for fiscal reasons in the face of strong political pressure , he seized the opportunity to close the post . The post was decommissioned on August 2 , 1886 ( S . O . No . 73 , Headquarters Department of Dakota , Fort Snelling , Minnesota ) and was abandoned by the Army by the end of August 1886 . After decommissioning , the parade ground was used for sometime by the Montana Militia . As of August , 1924 many of the fort ' s buildings remained intact , including a two - story house that was the Commanding Officer ' s quarters . That building today has been renovated and is occupied by the Agricultural Experimental Station operated by Montana State University .