Dawson County, Montana: History
Dawson County was the tenth county organized in Montana Territory. It was created January 15, 1869, four and a half years after Montana Territory was organized. Before the formation of Dawson county, the area was the northern half of the original Big Horn County. Dawson takes its name from Major Andrew Dawson, manager of the Fort Benton Trading Post for the American Fur Company from 1856 to 1864.
Between 1910 and 1920 the population increased from 2,500 to 25,000.
Parts of Dawson County were taken to form Valley County in 1893, Richland County and part of Wibaux County in 1914, part of Prairie County in 1915, and Garfield County and part of McCone County in 1919.