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, Idaho, United States is located in the northern most portion of the Idaho Panhandle with the northern end of the lake extending north to within 15 miles (24 km) of the Canadian border. The history of the lake dates back almost 10,000 years to the end of the last ice age. After the vast glaciers that covered most of the area receded and vegetation started to re-grow, humans started to resettle the area. This is evident from historical artifacts found in the area and ancient rock art along the lake.
The first white settlers arrived in the early 1800s. These early settlers were mainly fur trappers who quickly established trade with the native Kalispel Tribe. Jesuit Priests would eventually settle the lake in the 1840s and establish a base camp at Kalispell Bay. One of these priests, Father Pierre-Jean DeSmet, a native Belgian who had escaped from European persecution and became the most trusted of the white men among the Western Native Americans, named the lake Roothaan Lake for one of his superiors in Rome. The name would not stick though and in 1865 Captain John Mullan, a U.S. Army Captain who was traveling through the area under orders to build the "Mullan Trail" from Walla Walla, Washington to Fort Benton, Montana after the discovery of silver in the central Idaho mountains along what today is the route of Interstate 90, would re-name the lake Kaniksu. Kaniksu is believed to be the native word for “black robe” and because of the Jesuit presence the lake was later named Priest Lake.