Thomas Jefferson Heard, physician and soldier, the son of John and Susan (Fannin) Heard, was born in Morgan County, Georgia, on May 14, 1814. His mother was a cousin of James W. Fannin, Jr. He received his early education in his home county before attending medical school in Lexington, Kentucky. He moved to Texas in 1837 and established a practice at Washington-on-the-Brazos but almost immediately became involved in the region's Indian wars. He campaigned against Indians in 1838, 1841, and 1842 and participated in the repulse of Adrián Woll in 1842. In 1839 he married Frances A. Rucker of Washington County. In 1855 he was named president of the Brazos River Improvement Association.
In 1857 Heard moved to Galveston, where his medical practice flourished. During the Civil War he served as medical examiner on the staff of Brig. Gen. Thomas B. Howard, commander of Brigade Number One of Texas State Troops. He and Ashbel Smith were Sam Houston's attending physicians at the time of his death. Later Heard served on the faculties of the Galveston Hospital and Medical College and Tulane University in New Orleans. He was a founder of the Texas Medical Association and served for two terms as its second president, from 1868 to 1870.
Heard was a staunch advocate of the establishment of a state medical school and a medical journal. In 1852 he published "The Diseases of Washington, Texas for 1851" in the Transactions of the American Medical Association. In 1868 he wrote a history of epidemic diseases in the state, Report on Medical Topography, Meteorology, and Epidemic Diseases of Texas. In 1876, with Ashbel Smith and John Henry Bowers, he prepared a medical history of Texas, now in the Texas State Archives, but no evidence indicates whether the paper was delivered to the International Medical Congress in Philadelphia for which it was written. Heard was a Mason and a Democrat. He died on March 8, 1899.