Kalispell is a city in, and the county seat of, Flathead County, Montana. The 2010 census put Kalispell's population at 19,927, up 5,704 over 2000. At 40.1%, this is the largest percentage of growth of any incorporated city in Montana. Kalispell is the largest city and commercial center of northwest Montana. The name Kalispell is a Salish word meaning "flat land above the lake".