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.
During this time, he participated in the Black Hawk War as captain of a volunteer company.
Jenkins resigned mid-way through his term to become President of the Illinois Central Railroad.
He was later Receiver of Public Moneys at the United States General Land Office in Edwardsville, Illinois and was a delegate to the Illinois state constitutional convention from Jackson County in 1847.