The current Montana State Prison occupies a campus 3.5 miles (5.6 km) west of town.

The Grant-Kohrs ranch was built in 1862 by Johnny Grant, a Scottish/French/Metis fur-trader and trapper who encouraged his people to settle in Deer Lodge because of its pleasant climate and large areas of bunch grass prairie, ideal for raising cattle and horses.

The city's name derives from a geological formation known as Warm Springs Mound which contained natural saline that made for a natural salt lick for the local deer population, the protected valley in which Deer Lodge is located was where most of the local wildlife would winter as the temperatures lowered in the high country.

Extant mentions of the Deer Lodge Valley prior to 1860 are found as occasional remarks in records written for other purposes.

[11][12][13][a] 1860 marks the beginning of permanent occupation of both the valley and the future site of the city of Deer Lodge by European-Americans.

[17] American Indian groups from the west, Flatheads, Pend d'Oreilles et al. passed through the valley as an alternative route to and from the buffalo hunting grounds to the east.

[18][19] The first documented visit to this area by European-American explorers occurred in 1805–1806, when Lewis and Clark's Corps of Discovery expedition passed by the Deer Lodge Valley without entering it.

[20] Evidence of earlier incursion, probably by Spaniards, was noted by miner James B. Beattle on Sugar Loaf mountain in the Race Track mining district[21] on the west side of the Deer Lodge Valley.

[24][b] European-American settlement of the valley gained momentum during the 1850s and 60's, with the primary site being at present-day Deer Lodge.

[25] Also during that decade placer gold finds were made near present-day Gold Creek, first in 1852 by Francois (Bennetsee) Findley, followed in 1856 by Hereford, Saunders, Madison et al.,[26] and in 1858–61 by James and Granville Stuart, Reese Anderson et al.[27] In 1860–62, Lt. John Mullan oversaw construction of the Mullan Road, which connected Walla Walla, Washington Territory with Fort Benton, then in Dakota Territory.

John Francis (Johnny) Grant built the first permanent structures in the valley in 1859–60, at Grantsville near present-day Garrison.

[15] Grant had begun grazing cattle and horse herds in the north valley several years previously and "wintered over" there in 1857–58.

[c] Instead of locating at Grantsville, his friends chose to build at the site of present-day Deer Lodge, where several Mexican trapper/traders and their Metis families had already established the seasonal settlement of Spanish Fork.

[33][f] In 1861, the Stuart brothers and Reese Anderson established American Fork near present-day Gold Creek.

[34][g] During the next two years, placer gold discoveries at Grasshopper Creek, Alder Gulch and other locations to the south caused a population decline in the valley, including the abandonment of Grantsville and American Fork.

[35] Beginning in 1864 with gold strikes to the north, Deer Lodge City grew rapidly as a base for supplies to mines in the surrounding mountains.

[37][41] During the first half of the 1860s, Granville Stuart described valley social life as including many gay dances and parties,[42] which was the way of the Metis.

[44] In that year, Grant sold most of his Deer Lodge Valley holdings to Conrad Kohrs and in 1867 led a mass exodus of Metis families to the Red River country of Manitoba, Canada.

Clagett's partner, William W. Dixon, later moved to Butte and upset Thomas H. Carter in 1891 to serve a single term as U.S. Representative from the State of Montana.

This resulted in the MacDonald Report, which would be used as the basis for a civil lawsuit by the State of Montana against Conley.

[66] When he resigned for the last time, an article in the Billings Gazette called him 'the longest serving mayor in American history'.

Mayor Conley was instrumental in bringing the division headquarters and shops of the Milwaukee Road to Deer Lodge City in 1910.

[citation needed] In 1908, inmates W. A. Hayes and George Rock killed guard John Robinson and seriously wounded Warden Conley in an attempted prison breakout.

[74][75] As a result of legal actions begun in 1983 and culminating in 2008, the course of the Clark Fork River from Anaconda to the Milltown Dam was declared to be a Superfund cleanup site.

[78][u] According to the United States Census Bureau, the city has a total area of 1.44 square miles (3.73 km2), all land.

This climatic region is typified by large seasonal and diurnal temperature differences owing to its high elevation and dry conditions throughout the year.

[92] The school currently competes athletically in the 6B conference with Superior, Missoula Loyola, Valley Christian, Darby and Florence.

"It was built "for $30,000 by pioneer cattle baron Conrad Kohrs and his wife Augusta as a memorial to their son.

[97] Deer Lodge has been a filming location for a number of movies including: In a 2004 documentary titled The Secret of Redgate by Lynda J. Cowen and Jim Marrs, a number of Deer Lodge residents explain about their experiences with extraterrestrial beings and the rumours surrounding these events.

These occurrences which date back some fifty years took place at a location named Redgate on the eastside of Deer Lodge.