Background
He was born on August 5, 1885, in Brooklyn, the son of John Gillen (1853–1924) and Margaret Nancy (McGrath) Gillen (1860–1944).
He was born on August 5, 1885, in Brooklyn, the son of John Gillen (1853–1924) and Margaret Nancy (McGrath) Gillen (1860–1944).
He attended the public schools.
He engaged in the real estate and insurance business. He died on February 1, 1942, in Brooklyn, of a heart attack. And was buried at the Holy Cross Cemetery there.
Gillen was a member of the New York State Assembly (Kings Company, 3rd Doctorate) in 1926, 1927, 1928, 1929, 1930, 1931, 1932, 1933, 1934, 1935, 1936, 1937, 1938, 1939-1940 and 1941-1942.