Gulick was born in Kansas City, Missouri. According to his autobiography, his grandmother wanted him to be named after his father, as Grover Cleveland Gulick, Jr.; but his mother resisted fiercely, and they eventually compromised with Grover C. (only) Gulick, "with my Mother saying I could choose my own middle name when I became old enough to do so." He later acquired the nickname 'Bill'.
He graduated from Classen High School in Oklahoma City, Oklahoma in 1934. The following September, he attended the University of Oklahoma.
Gulick had numerous short stories and 20 novels published, of which three have been made into movies.His book Snake River Country won the 1971 Pacific Northwest Booksellers Award as Best Non-fiction Book.