He was born at Neely's Bend in Davidson County, Tennessee, on a farm that had been in his family since the eighteenth century.
[2] After graduating from high school, he started working for the Cumberland Telephone Company.
In 1908, he began working for the Southern Lumberman, a trade paper on the lumber business.
[2] Horn served as president of the Tennessee Historical Society for fifteen years (1942-53, 1961-65).
When Horn retired from the Tennessee Historical Commission, Governor Buford Ellington appointed him state historian.