McCulloch was born near Holmesville, Ohio. He attended the College of Wooster in Wooster, Ohio. He graduated from the college of law of Ohio State University at Columbus, Ohio, in 1925. He was admitted to the bar the same year and commenced practice in Piqua, Ohio. He was a member of the Ohio House of Representatives from 1933 to 1944, serving as minority leader from 1936 to 1939 and as speaker from 1939 to 1944. He served in the United States Army from December 26, 1943, to October 12, 1945.