His first clash with General Andrew Jackson followed Jackson's 1818 invasion of Florida during the First Seminole War. While praising Jackson's character, Tyler condemned him as overzealous for the execution of two British subjects. Tyler was elected for a full term without opposition in early 1819.[25]
The major issue of the Sixteenth Congress (1819–21) was whether Missouri should be admitted to the Union, and whether slavery would be permitted in the new state.[26] Acknowledging the ills of slavery, he hoped that by letting it expand, there would be fewer slaves in the east as slave and master journeyed west, making it feasible to consider abolishing the institution in Virginia. Thus, slavery would be abolished through the action of individual states as the practice became rare, as had been done in some Northern states.[26] Tyler believed that Congress did not have the power to regulate slavery and that admitting states based on whether they were slave or free was a recipe for sectional conflict;[27] therefore, the Missouri Compromise was enacted without Tyler's support. 