Horace Maynard was born on August 30, 1814 in Westboro, Massachusetts. He graduated from Amherst College as valedictorian in the summer of 1838 and came to East Tennessee College (now the University of Tennessee, Knoxville) to teach in the fall. He was quickly promoted, first to teacher of Mathematics and Ancient and Modern Languages and later to Professor of Rhetoric and Belles-Lettres. In 1840, Maynard began writing a series of articles for the Knoxville Times under the pen name Zadock Jones. He also studied law; he was admitted to the Bar and commenced practicing in 1844.

Maynard also involved himself in politics. He served as presidential elector twice, first on the Whig ticket in 1852 and then on the Republican ticket in 1856. He was unsuccessful in his first bid for national office in 1853 but was elected to the U. S. House of Representatives in 1857. He was re-elected twice and served until Tennessee seceded from the Union. He went on to serve as the Attorney General of Tennessee (1863-1865) and as a delegate to the Southern Loyalist Convention in Philadelphia (1866).

After Tennessee was readmitted to the Union, Maynard was once again elected to the U.S. House of Representatives. He served until 1875, but chose not to run for re-election in 1874 in order to campaign (unsuccessfully) for the governorship of Tennessee. President Ulysses S. Grant appointed him U.S. Ambassador to Turkey in 1875, and he remained at this post until May 1880. President Rutherford B. Hayes appointed him Postmaster General in June 1880, and he served until 1881.

Maynard married Laura Ann Washburn (1813-1896), daughter of Azel and Sally Skinner Washburn, in 1840. Together, Horace and Laura had seven children: Edward (1843-1868), Washburn (1844-1913), Eleanor (1846-1848), Ephraim Horace (1848-1850), Laura (1851-1852), James (1853-1926), and Anne Mary (Maynard) Kidder (1856-). Maynard died in Knoxville, Tennessee, on May 3, 1882 and is buried in Old Gray Cemetery.