Montana was home to many indigenous people before it was claimed by the Spanish, French, and other European people. The United States acquired the part east of the Continental Divide as part of the Louisiana Purchase in 1803, and the Wester portion was acquired from Great Britain in 1846.  It was governed by various territorial jurisdictions before becoming the forty-first state in 1889.  If your ancestors lived there before statehood, you may want to request records from the Oregon Territory, Idaho Territory, or Montana Territory.

The eastern part of the state is plains, and the western part is mountainous. This includes part of Yellowstone National Park. The state shares its northern border with Canada. Montana's wealth comes largely from ranching, mining, and tourism. The state is sometimes called the Treasure State or Big Sky Country.

This guide offers a selection of resources and strategies for Montana local history and genealogy research. These include the print and digital collections of the Library of Congress, as well as external repositories and web sites key to finding forebears in the Big Sky Country.