Hardin opened a law practice in
Fulton, Missouri in 1843. From 1848 to 1852, he was a circuit attorney for the Second Judicial Circuit of Missouri. He served in the
Missouri House of Representatives, with terms starting in 1852, 1854, and 1858. He was a
Democrat. He was a member of the commission that revised and codified the state's statute laws. In 1860, he was elected to the
Missouri Senate 9th District, with a term lasting until 1862. As a state senator, he attended
Claiborne Fox Jackson's secessionist meeting in
Neosho, Missouri and was the only senator present to vote against
secession. During the Civil War, he returned to the family farm in
Audrain County, Missouri in 1862. After the war, Hardin and his family moved to
Mexico, Missouri, where he established a new law practice and co-founded Mexico Southern Bank following the close of the war. In 1872, Hardin was again elected to the state senate for a term lasting until 1874. In 1876, he was a delegate to the Democratic National Convention from Missouri. He ran for governor of Missouri and was elected on
November 5, 1874. He served as
22nd Governor of Missouri between January 1, 1875, and February 8, 1877. During his term, a new constitution was approved. Hardin also reduced Missouri's debt from the Civil War and state funding for railroad expansion by ending wasteful practices and refinancing bonds. Hardin established
Hardin College and Conservatory of Music in
Mexico, Missouri. In 1873, Hardin gave land worth $60,000 to the college and afterward served as the president of its board. == Personal life ==