[2] Originally Tharp, it was named in 1915 (or earlier)[3] after the Fenn family.

[4] Stephen S. Fenn (1820–92)[5] arrived in Florence from California in 1862 with his wife and four children.

His son, Major Frank A. Fenn (1853–1927),[7] also of many professions, was the speaker of the first state legislature.

[4][8][9] An earlier settlement a few miles north, Denver, was mostly abandoned after the Camas Prairie Railroad bypassed it.

A grain elevator was constructed in Fenn in 1918,[10] and an upgrade was added in 1946,[11] served by the railroad until the abandonment of its Second Subdivision line to Grangeville in late 2000.