This building / tower is one of the more visible landmarks in downtown Great Falls. The sign at the top suggests "Chicago Milwaukee & St. Paul RY" but apparently it is being used as an office building.
Below is the sign that shows the tenants.
The sign reads:
RBC Dain Rauscher
Davis, Hatley, Haffeman & Tighe, P.C. Attorneys At Law
Grabofsky, Van Heel & Funderburk, P.C.
High Plains Pizza, Inc.- Big Sky Region
McDonald's of Great Falls
Chicago Title Insurance Company
Important NOTE, this picture was taken somewhere around 2008 so chances are there have been changes to the above list.