Born in Bridgewater, Maine in 1880, Nathaniel Thompkins was educated at Ricker Classical Institute, Colby College and Harvard Law School before practicing law in Houlton.
Chairman of the Board of Selectmen of Houlton in 1912 and 1913, he was a member of the Maine House of Representatives in 1931-1932, 1933-1934 and 1935-1936 when he served as Speaker.
In 1938 he was elected to the Maine Senate for the 1939-1940 term and reelected in 1940 for the 1941-1942 term during which he served as that body’s President.
Prior to the 1942 Special Session, Thompkins resigned his seat.