Born in
Sandwich,
Illinois, Castle was in the
United States Army towards the end of
World War I, in 1918, and then received a
Bachelor of Laws from
Northwestern University Pritzker School of Law in 1924. He was in private practice in Sandwich from 1924 to 1925, and was a city attorney of Sandwich from 1925 to 1928, becoming a corporation counsel of
Sycamore, Illinois in 1928. He was then a state's attorney of
DeKalb County, Illinois from 1928 to 1940, becoming an assistant state attorney general of Illinois from 1940 to 1942. He was a County judge for DeKalb County from 1942 to 1952. He served as Attorney General from January 12, 1953, until May 8, 1959. He was succeeded as Attorney General by
Grenville Beardsley. ==Federal judicial service==