Brown was a native of Virginia, but a graduate of the University of North Carolina at Chapel Hill where he was valedictorian of the class of 1814. He later entered into the practice of law with James K. Polk. He was a member of the Tennessee State Senate from 1821 to 1827 and of the Tennessee House of Representatives from 1831 to 1835, and a member of the United States House of Representatives for three terms, 1839 to 1845. He won the Democratic nomination for governor in 1845 and was elected.

When the Mexican War began, largely through the actions of his old friend Polk, who was now President, Brown issued a call for 2,600 volunteers. When approximately 30,000 men answered this call, Tennessee's reputation as the Volunteer State was forever secured.

Like his friend Polk, Brown was also defeated for re-election as governor of Tennessee. He did not participate further in statewide elected politics, but was selected as a delegate to the Southern Convention of 1850 held at Nashville's Maxwell House Hotel. This is probably the first place in Southern history where secession was ever openly and seriously discussed outside of South Carolina. Some historians credit the pressure that it instigated as helping to lead to the Compromise of 1850. Brown was subsequently rewarded for his service as a loyal Democrat by being appointed Postmaster General and was still holding this office at the time of his death. He is buried in Nashville's Mt. Olivet Cemetery.

Governors of Tennessee Sevier • Roane • Sevier • Blount • McMinn • Carroll • Houston • Hall • Carroll • Cannon • Polk • Jones • A Brown • N Brown • Trousdale • Campbell • Johnson • Harris • Johnson • East • Brownlow • Senter • J Brown • Porter • Marks • Hawkins • Bate • R Taylor • Buchanan • Turney • R Taylor • McMillin • Frazier • Cox • Patterson • Hooper • Rye • Roberts • A Taylor • Peay • Horton • McAlister • Browning • Cooper • McCord • Browning • Clement • Ellington • Clement • Ellington • Dunn • Blanton • Alexander • McWherter • Sundquist • Bredesen