B. bifarius inhabits mountainous regions of western North America, primarily the states of Colorado and Utah.

[3] Bombus bifarius was first described by Ezra Townsend Cresson in the 1878 Proceedings of the Academy of Natural Sciences of Philadelphia.

[4] Red-tailed specimens classified as B. bifarius are found from Colorado all the way north to British Columbia, but have been found to comprise two different species (bifarius and Bombus vancouverensis) while the nearcticus color pattern, primarily found in western Canada, Alaska, California, Oregon, Idaho, Montana, and Washington, belongs to vancouverensis and not to bifarius.

[3][5] Because of differences in genetic structuring between these populations in various geographic locations, there had been debate as early as 2013 suggesting these two major color pattern polymorphisms might represent more than one biological species.

[5] Bombus bifarius is found in mountainous regions of western North America, limited to northern Arizona, Colorado, northern New Mexico, Utah, and southern Wyoming; populations from all other areas formerly classified as bifarius belong instead to B.