Born to Dr. Issac Jennings and Nancy Ann Beach, he removed with his family in 1839 to Oberlin, Ohio, and thence to Cleveland, Ohio in 1849. He was very involved in real estate and insurance. He lived on Jennings Road and undoubtedly named the street. Part of Jennings Road later became West 14 Street. Thyrza Pelton and John Giles Jennings bought up 275 acres (1.11 km2) of land from local farmers with the intent of creating a new university; however, most of this land would later be sold off to raise funds for the school, Cleveland University. He created the University Heights allotment in 1851. Mr. Jennings taught Sunday school in 1859-1860. The people of the area wanted their own church rather than traveling east of downtown and meetings were held at the home of John Jennings on Scranton Avenue. On November 13, 1859, University Heights Congregational Church was founded. When a new church building was added in 1869, this church was named Jennings Avenue Congregational Church after the street which was named after Mr. Jennings. Mr. and Mrs. Jennings were generous to the church and he was a deacon of the church for more than 25 years. He was also a Founding Trustee of Riverside Cemetery and is buried in Section 5.