Jenkins settled in Jackson County, Illinois as a youth, residing in Brownsville. He engaged in trade before studying law and practiced his profession in Southern Illinois. He was elected to the Illinois House of Representatives in 1830 and 1832, serving as Speaker in his second term. During this time, he participated in the Black Hawk War as captain of a volunteer company. In 1834, he was elected Lieutenant Governor as a member of the Democratic Party, serving under Governor Joseph Duncan, a Whig. Jenkins resigned mid-way through his term to become President of the Illinois Central Railroad. He was later Receiver of Public Moneys at the General Land Office in Edwardsville, Illinois and was a delegate to the Illinois state constitutional convention from Jackson County in 1847. In 1859, he was elected Circuit Judge for the Third Judicial Circuit and was re-elected in 1861. He died on February 13, 1864.
