After visiting the La Grange College Clemens in 1833 graduated from the University of Alabama in Tuscaloosa. He then studied law at Transylvania University in Lexington (Kentucky), was admitted to the bar in 1834 and commenced practice in Huntsville. In 1838 he was appointed United States Attorney for the Northern District Court of Alabama.
In the following years, political and military activities alternated. He was from 1839 to 1841 and from 1843 to 1844 a member of the House of Representatives from Alabama interrupted by an insert in the Texas War of Independence. During the Mexican-American War, he fought with the rank of Lieutenant Colonel in the U.S. Army.
In 1848, Clemens applied unsuccessfully for a seat in the U.S. House of Representatives. The following year he was elected for the U.S. Senate, to take the place of the late Dixon Hall Lewis. Clemens remained there on 30 November 1849 to 3 March 1853.
As a result, Jeremiah Clemens devoted, who was a cousin of Mark Twain (born Samuel Clemens ), his literary activity. He wrote several novels, including "A Tale of the Times of Aaron Burr and Alexander Hamilton " and " Tobias Wilson, a Tale of the Great Rebellion ". In 1858, he moved for a year to Memphis, where he worked for a newspaper; after his return to Alabama in 1861 he was a delegate to the Secession Convention of the state. He has held several offices under the Confederate government, declared in 1864 but his support for the Union. The following year, Clemens died in his native Huntsville.