Forest Grove's first post office was established in 1899 with Thomas Frost as postmaster. It was closed in 1900 and reopened in 1904. In the 1920s and 1930s, coal mines were worked in the area, and with the help of mules, the coal was then pulled to ore cars to be shipped out on the Milwaukee Railroad line. In 1918, the population grew to 525. Today, only the post office and the wool shop of postmaster May Charbonneau remain.
Forest Grove is located in central Montana, northeast of Lewistown.