He was a lieutenant in the United States Naval Reserve during World War II, from 1942 to 1946.

He was a law clerk to Judge Charles Casper Simons of the United States Court of Appeals for the Sixth Circuit from 1946 to 1947, and was then in private practice in Detroit, Michigan from 1947 to 1951.

He was a special Assistant United States Attorney for the Eastern District of Michigan from 1951 to 1952, returning to private practice from 1953 to 1954.

[1] On May 22, 1980, Gilmore was nominated by President Jimmy Carter to a seat on the United States District Court for the Eastern District of Michigan vacated by Judge Cornelia Groefsema Kennedy.

He was confirmed by the United States Senate on June 18, 1980, and received his commission the same day.