Hambletonian 10 was bred by Jonas Seely, Jr. on his farm at Sugar Loaf in Orange County, New York. He was sired by Abdallah who was a grandson of the hugely influential Thoroughbred sire, Messenger. Abdallah was ugly in body and temperament, so much so that he was sold to a fish pedlar for $5. Hambletonian's dam was known as the Charles Kent Mare or the "Kent Mare" by Bellfounder (GB), an imported Norfolk Trotter. Hambletonian was inbred to Messenger (GB) (1780) in the third and fourth generations (3x4x4x4).