Jackson first learned the law under Spruce Macay in Salisbury, North Carolina. He later traveled to McLeanville, North Carolina, where he set up his own law practice. In 1788, he and friend John McNairy traveled to what later became Tennessee and practiced what was sometimes known as “frontier law.” They also prospered with land speculating.

McNairy became a judge and he appointed his friend Jackson as Solicitor of the Western District and later Solicitor of the Territory of Tennessee. In 1798, he was appointed to the Tennessee Supreme Court, where he served until 1804.