Sanders County Montana contains within its borders an historical section of the Clark’s Fork of the Columbia River. This river was a main thoroughfare for Native Americans in the North West who used it to pass out onto the plains in pursuit of buffalo.

By 1809 the North West Company fur trader and cartographer, David Thompson, had traveled up the Clark’s Fork River, creating a map for his company. By 1810 Thompson had established the widely known fur post known as Saleesh House. In 1821 the North West Company and the Hudsons Bay Company merged and all of the NWC fur trade and posts were then operated under the name of the Hudsons Bay Company.

In the early 1850s, Governor I. I. Stevens had been given and executed a commission to explore near the 47th and 49th Parallel in an effort to determine the best route for a railroad to the Pacific. His official report ended by recommending the Clark’s Fork River to traverse the mountains and by the 1880s the Northern Pacific Railroad was operating along the Clark’s Fork River. Miners and settlers flooded in to the new country in search of a new life.

Many small towns sprung up along the tracks and one of the settlements that endured was the little town of Thompson which was to become known as Thompson Falls. The town itself was a ‘jumping off’ point for miners and supplies heading over the mountains into the gold mines of Idaho. The early development of logging and farming insured that the little town survived and continued to expand.

By 1906 Sanders County was formed and Thompson Falls became the county seat. Six years later a dam was under construction across the Clark’s Fork at Thompson’s Falls and the town of Thompson was firmly established with a combination sheriff’s office, jail and residence completed in 1907 with the dam basicly completed by 1917.

The Old Jail was scheduled for demolition by the late 70s and in 1980 a charter was obtained by concerned citizens to form the Sanders County Historical Society. This Historical Society took over the maintenance of the original Old Jail and started in earnest to restore the building.

Today the Old Jail Museum is a going concern that is open daily from Mother’s Day to Labor Day with many exhibits. The Sanders County Historical Society continues to conserve the history of Thompson Falls and the Valley of the Clark's Fork, following faithfully its mission statement:

“The Sanders County Historical Society shall promote and foster such activities as draw together, preserve and display items of historical significance to Sanders County and contiguous geographic areas, for the enjoyment and enrichment of all interested people.”