Fort Mackenzie was established in Sheridan in 1898 as a U.S. Army outpost in northern Wyoming.

Established 24 years after the Battle of Little Bighorn and after nearby military posts in Montana had been abandoned, the fort was regarded as a pork-barrel project instigated by Wyoming's Congressional delegation following Wyoming statehood in 1890, rather than as a project driven by military requirements.

[4] There are 48 structures listed as contributions to the Fort Mackenzie National Register of Historic Places district.

The campus represents a uniform community of red brick hospital buildings, residences and supporting with simplified neoclassical detailing.

The ensemble presents a homogeneous complex comparable to those of Fort Yellowstone or the original army post at Francis E. Warren Air Force Base.