The mule deer is endemic to North America and occurs in all of the continent’s western biomes north of central Mexico, except the Arctic tundra.
The mule deer occurs over most of North America, west of the 100th meridian from 23 degrees to 60 degrees North.
In western North America, the mule deer occurs from Alaska and Western Canada through the Rocky Mountains and Western Plains States of the United States south to the Peninsula of Baja California, Cedros Island, Tiburon Island and Northwestern Mexico.
The eastern edge of the usual range extends from southwestern Saskatchewan through central North and South Dakota, Nebraska, Kansas, and western Texas.
The southernmost distribution reaches central Mexico, but the historical boundary is not very clear.
Major gaps in geographic distribution are in southern Nevada, southeastern California, southwestern Arizona, and the Great Salt Lake desert region. Isolated occurrences have been reported from Minnesota, Iowa, and Missouri.
Apart from these gaps, mule deer occur in all of the biomes of western North America north of central Mexico, except the Arctic tundra.