Denny was elected to the first branch of the Baltimore City Council in 1881, was reelected in 1882, and later became its president. He also served in the Maryland House of Delegates from 1888 to 1890, as colonel on the staff of Gov. Elihu Emory Jackson and as member of the Baltimore School Board for eight years.[1]
Denny was elected as a Democrat to the fifty-sixth congress (March 4, 1899 – March 3, 1901), but was an unsuccessful candidate for reelection in 1900 to the fifty-seventh congress. He later was elected to the fifty-eighth congress (March 4, 1903 – March 3, 1905).[3] He engaged in the practice of law until his death.[1]