Wild Horse Plains is nestled in a circular valley at an elevation of 2,450 ft., drained by the Clark Fork River. Between 70,000 and 130,000 years ago the Bull Lake ice age glaciers dammed the Clark Fork River Valley creating Glacial Lake Missoula. All of the waters from the Clark Fork River drainage backed up to form a Lake. When the ice dam broke, the Clark Fork River carried more water than the combined flow of all the streams of the world.

In the early 1800's Native American tribes traveled through the area. The fertile valley was used for wintering their ponies, harvesting salmon, and holding great councils. Mountain men, trappers, surveyors, and map makers were soon to follow.

White settlers began their movement in the valley in the late 1860's. During the decades to follow farming, ranching, and lumbering would flourish in the valley.

The Northern Pacific Railway arrived in 1881-1883 and the town began to increase in size and importance. Businesses flourished and eventually the name was shortened to Horse Plains and finally to Plains