The Spion Kop wind farm will consist 25 units of 1.6MW GE wind turbines near Geyser, Montana.
Construction is set to commence in late 2012, and the facility is due to be completed by the end of the year.
The Montana Public Service Commission approved placement of the $86.1m project into the company’s regulated rate base in mid-February.
Under Montana’s Renewable Portfolio Standards, 15% of NorthWestern Energy’s total energy portfolio must be produced from renewable generation by 2015.
NorthWestern Energy provides electricity and natural gas in the Upper Midwest and Northwest, serving about 668,300 customers in Montana, South Dakota and Nebraska.
