A prolific comic book writer, he created such Charlton Comics heroes as Peacemaker, Judomaster, and Captain Atom. Later in his career, he worked for DC Comics.
He began his career at Timely Comics in New York City during the 1940s. A decade later, he became the main staff writer at Charlton Comics.
He collaborated in the 1970s with comic book artist John Byrne on the Doomsday + 1 series.
He was born in Scranton, Pennsylvania and grew up with a brother named Ray. He died at age eighty-seven, having survived both his wife and his son.
He was a close friend of hardboiled detective novelist Mickey Spillane. Spillane, in fact, convinced Gill to pursue a career in freelance writing.