Born in Port Hope, Ontario, Upper Canada, Belnap, the grandson of American Revolutionary War veteran Jesse Belnap, was orphaned at age 10-12. Attaching himself to an American company of light horse rangers as first sergeant, he was taken as prison-of-war in the Upper Canada Rebellion. Following his release, he eventually made his way to Kirtland, Ohio, where he was baptized a member of the Church of Jesus Christ of Latter Day Saints in 1842. Shortly after his baptism, he served a mission with John P. Greene to Upstate New York.