MISO stands for Midcontinent Independent System Operator.  MISO is a regional transmission planning organization whose area covers much of the Midwest and Great Plains.  MISO’s membership list includes ATC, Dairyland Power Cooperative, ITC Midwest, Alliant Energy, Madison Gas & Electric, and Wisconsin Electric Power Co. (https://www.misoenergy.org/StakeholderCenter/Members/Pages/MembershipList.aspx)