Stuart was already a lawyer by profession.

During the Black Hawk War he commanded one of the Sangamon County companies, and was soon afterward elected major of a spy battalion formed from some of these companies.

He had the best of opportunities at this time to observe the merits of Captain Lincoln, and testifies that the latter was exceedingly popular among the soldiers on account of his excellent care of the men in his command, his never-failing good nature, and his ability to tell more stories and better ones than any man in the service.

He was popular also among these hardy men on account of his great physical strength.

For several years after the Black Hawk War Lincoln retained his military title and was usually addressed as "Captain Lincoln." But this in time was discontinued.