Determined to secure reliable electricity for western and central South Dakota, five rural cooperatives (Black Hills Electric, Butte Electric, Lacreek Electric, West Central Electric, and West River Electric) unite in June of 1950 to form Rushmore G&T Cooperative (later renamed Rushmore Electric Power Cooperative). It is incorporated under the laws of the state of South Dakota and authorized to do business in Wyoming. It's mission: to furnish an ample supply of reliable electric energy to its member systems at the lowest possible cost and to continue to meet the present and growing needs of its members. 

Facing potential future power outages from its members' growing need for electricity, Rushmore partners with Black Hills Power & Light's (BHP&L's) Osage Power Plant to build a new 10,000-kilowatt coal unit for $2 million (operational in 1952). Three years later, in 1955, Rushmore begins constructing a new generator at BHP&L's Kirk Power Plant. When the plant comes online in 1956, it is the largest generating unit in South Dakota. It provides reliable electricity to thousands of homes and farms throughout the region, including those served by Tri-County Electric Association in Sundance, Wyoming. To deliver this power to the co-ops that need it, Rushmore leases BHP&L's transmission lines.

A new era begins as Missouri River dams—Ft. Randall, Gavin’s Point, Oahe (photo above), and Big Bend—come online, supplying Rushmore's co-ops with much-needed federal hydropower. In April 1954, the US Bureau of Reclamation completes construction of the first of several West River (west of the Missouri) transmission lines and begins delivering power to the Rushmore system. During this time, the Rushmore system's federal hydropower allocation increases from 10,000 kilowatts to 15,500 kilowatts.

Rushmore's 1955 Load Study, drafted to ensure reliable and adequate future electric supply, projects that the cumulative demand from all the co-ops it serves will reach 24,000 kilowatts by 1964.

In 1961, three years earlier than anticipated, the Rushmore system's demand reaches 23,800 kilowatts. To address future electric supply needs beyond what local generation and federal hydropower can provide, co-ops in eight states, including South Dakota (and Rushmore's co-ops), join forces to create Basin Electric Power Cooperative. This "super G&T" is established to leverage economies of scale to ensure reliable, affordable electricity for the rural Dakotas, Montana, Wyoming, Nebraska and neighboring states for generations to come. Prior to incorporating, the organizers of Basin Electric consider naming it "Giant Power Cooperative" and headquartering it in Rapid City. Basin's mission is similar to Rushmore's, but covers a larger geographic footprint: to supply all (electric supply) deficiencies of its member systems.

In June, Rushmore Electric forms a new subsidiary - Rushmore Federal Credit Union - to assist rural electric cooperative employees and directors with banking and financial planning needs.

On January 10, 1966, Basin Electric’s first power generating plant, Leland Olds Station, a $36 million 200,000-kilowatt generator, comes online in Stanton, North Dakota. It immediately helps Rushmore's co-ops by stabilizing the regional grid.

Growth continues as Cam Wal, Cherry-Todd, and Moreau-Grand cooperatives join Rushmore, expanding Rushmore's support services across South Dakota's heartland.

Rushmore Electric establishes a new subsidiary - Rushmore Engineering - to help its member cooperatives with distribution and transmission planning and design.

Assured of its future power supply and reliability from Basin Electric's generation fleet and Western Area Power Administration's (WAPA's) hydropower resources, Rushmore sells its interest in the Kirk Power Plant. The Rushmore system's federal hydropower allocation surpasses 35,000 kilowatts.

After purchasing Custer, SoDak-based Southern Hills Communications' assets, Rushmore Electric forms its third subsidiary - Rushmore Communications. The purchase includes the Bear Mountain Communications Tower and a robust inventory of radio and electronic equipment. The acquisition serves three purposes: to provide communications assistance to the distribution co-ops that own Rushmore Electric, to support Rushmore Electric's SCADA network, and to provide ongoing support for Southern Hills' existing clients.

Rushmore diversifies its power portfolio, sourcing 84% from all-of-the-above generation and transmission cooperative Basin Electric and 16% from the federal dams (marketed by WAPA).

Rushmore's demand response programs curtails 1.4 GW of peak demand over a 20 year period, saving its member co-ops $27 million in wholesale power costs.

Since 1950, Rushmore has been more than an electric provider—it’s been a powerful network of support, keeping communities strong, connected, and prepared for the future.