 McDiarmid Falls was named officially in 2000 and refers to Garfield (better known as Mac) and Cecile McDiarmid, a pioneer family of the Clearwater Valley.They moved to the area in 1944 and purchased 160 acres of land just south of Grouse Creek.In 1956 they purchased a separate property of 70 acres beside the Clearwater River and adjacent to both Moul Falls and McDiarmid Falls.