SPP used social media recently to announce its membership had hit 90 with the addition of three cooperatives and an investor-owned utility that joined the RTO as part of the Integrated System.

• East River Electric Power Cooperative is a wholesale supply cooperative serving 24 rural electric co-ops and one municipally owned electric system with a total of more than 92,000 homes and businesses. The cooperative has a 40,000-square-mile service area covering 63 primarily rural counties in eastern South Dakota and western Minnesota.
• Northwest Iowa Power Cooperative is a generation and transmission cooperative supplying wholesale power to seven distribution co-ops serving more than 30,000 members and consumers. It covers 6,500 square miles in western Iowa.
• Corn Belt Power Cooperative, another G&T cooperative, provides energy to nine distribution co-ops and a municipal co-op in 41 counties in northern Iowa.
• NorthWestern Energy is an investor-owned utility providing electricity and natural gas to about 692,600 customers in Montana, South Dakota and Nebraska. It owns and operates wind, water, natural gas and coal-fired generation and delivers electricity to more than 416,100 customers.

SPP began coordinating transmission for the Integrated System on June 1. Full membership is expected in October. SPP has members from 14 states and 48,537 miles of transmission; the newest members will give SPP approximately 60,000 miles of transmission, stretching from northwest Louisiana, across the Great Plains to western Montana.