A. False
Thomas Jefferson did not express support for the Missouri Compromise of 1820, nor did he believe that it had solved the issue of slavery once and for all. In fact, Jefferson wrote to John Holmes in 1820 expressing concern that the Missouri Compromise would only serve to temporarily ease tensions between North and South over the issue of slavery. Jefferson believed that the issue of slavery would continue to be a divisive one for the United States, and he expressed regret that the country had not dealt with the issue more definitively during the drafting of the Constitution.