He was born on December 5, 1866, in Oakville, Canada West the son of Edward Hillmer and Jean Titherington. Hillmer originally operated a delivery service and livery stable but later became the proprietor of a Ford agency. In 1894, he married Pauline Bradbury. Hillmer was a member of the town council for Oakville, serving as mayor from 1910 to 1912 and serving eight years as reeve. He defeated Ernest Charles Drury to win a seat in the provincial assembly in 1923. Hillmer was a Master Mason.