John Thompson Flint, attorney, banker, Texas legislator, trustee of Waco University, and Confederate veteran, was born in Schoharie County, New York, on April 2, 1827. He was the son of Isaac Flint (1792–1865) and Abigail Harriet (Delesdernier) Flint (1798–1865). He received a liberal education and later taught school. He left New York and relocated to Portsmouth, Ohio, where he began reading law under O. F. Moore in 1850. Flint was admitted to the bar of the Supreme Court of Ohio in 1852 and began the practice of law. On March 9, 1854, he married Lavina H. Feurt (1830–1876) in Scioto County, Ohio, and the couple had three known children—Mary, John Fort, and Harriet (who was later the wife of John R. Frazier).
In December 1852 Flint moved to Austin, Texas. An excellent stenographer, he became a candidate for the position of reporter of the Texas Senate. He was elected to this office in January 1853. Later that year, he relocated to Belton, Bell County, Texas, where he began practicing law until 1865. John T. Flint served as a representative of Bell and Lampasas counties in the House of the Ninth Texas Legislature from November 1861 to November 1863. During his term he served on several committees, including the Confederate Relations, Penitentiary, and Land Office committees. Flint served in the Twentieth Texas Confederate Infantry, Company D, during the Civil War. In 1865 he served as the district attorney of McLennan County, Texas, where he resided with his family.
In 1866 Flint and David Tolles Chamberlin established the banking house of Flint & Chamberlin in Waco. That same year Flint was listed on the board of trustees for Waco University. He formed a law partnership with Evander Hugh Graham, and the firm was known as Flint & Graham in Waco. In the late 1860s Flint served for five years as the president of the Waco Bridge Company, which was responsible for the construction of the Waco Suspension Bridge across the Brazos River. He became president of the Waco and Northwestern Railroad Company/Waco Tap Railroad Company in November 1869.
Flint continued to practice law in Waco, and city directories show that by 1890 he practiced law with his son John Fort as the firm of Flint & Flint. In 1894 he was listed as the proprietor of Waco Dairy Company. John Thompson Flint died on January 16, 1897, in Waco and was buried in the Flint family plot at the First Street Cemetery, Waco.