Sun River Electric Cooperative was first organized as Sun River Electrification Corporation on April 10, 1937 at a meeting in the courthouse in Great Falls, Montana. A Board of Directors consisting of S.F. Hackersmith, J.J. Morris, A.L. Meyer, C.G. McDermott, Knut Knutson, P.L. Hame, and Hy Hanson authorized a $100,000 loan from the Rural Electrification Administration to build power lines to rural residents in Cascade and Teton Counties.

In November of 1937 an office was rented in the Simms Bank Building and was furnished with a rented desk, chair, typewriter and file cabinet. The Sun River Electric office was moved to Fairfield in May of 1938, where an office space was rented also. A building and land were later purchased, this is the same location as the existing office building.

The first electric service was installed in the Sun River Valley from Vaughn to Simms and north to the Fairfield Bench. Today Sun River Electric serves consumers in Cascade, Teton, Pondera, Lewis & Clark, Chouteau, Liberty, Toole, and Judith Basin counties. The main headquarters are located in Fairfield. There are two outposts with three linemen located in Conrad and two linemen located in Highwood. Sun River Electric currently has twenty-two employees. The Board of Directors consists of seven members, Leonard Sivumaki, Russ Bloom, John Burgmaier, Bryce Johns, Chris Music, Mitch Johnson, and Robert Pasha.