Flathead Lake was first described by explorer David Thompson as _A fine sheet of water_. It_s that—-and much more. The largest natural freshwater lake west of the Mississippi is 28 miles long and up to 15 miles wide, providing 188 square miles of pure pleasure! The lake_s pure sparkling waters and miles of tree-lined shore offer unlimited recreational opportunities and wildlife habitat. Overlooking it all are the magnificent Swan and Mission mountain ranges.