He studied law under Rufus Easton, who was Missouri Territory's second representative to Congress.

After being admitted to the bar, he and Edward Bates, Missouri's first attorney general, formed a law firm.

[1] Barton was the first Secretary of State, but resigned to become district attorney of St. Louis, Missouri.

[2] William Rector had previously been hired to survey the location route of the Buffalo Trace before an Indian treaty line was established.

[3] Joshua Barton made the charges in a letter signed "Philo" to the weekly newspaper the St. Louis Republican.