He was a chief assistant and acting District Attorney of Bronx County, New York from 1924 to 1947.
[1] Ryan received a recess appointment from President Harry S. Truman on November 1, 1947, to a seat on the United States District Court for the Southern District of New York vacated by Judge Francis Gordon Caffey.
He was nominated to the same seat by President Truman on November 24, 1947.
He served as Chief Judge from 1959 to 1966 and as a member of the Judicial Conference of the United States from 1959 to 1968.
Ryan served in that capacity until his death on April 10, 1981, in New York City.