King found that a constitutional convention was already underway, and by October 1849, the convention unanimously agreed to join the Union—and to ban slavery within their borders.[115]

United States states (Texas border unsettled, California admitted in 1850) and territories during Taylor's presidency
The question of the New Mexico–Texas border was unsettled at the time of Taylor's inauguration. The territory newly won from Mexico was under federal jurisdiction, but the Texans claimed a swath of land north of Santa Fe and were determined to include it within their borders, despite having no significant presence there. Taylor sided with the New Mexicans' claim, initially pushing to keep it as a federal territory, but eventually supported statehood so as to further reduce the slavery debate in Congress. The Texas government, under newly instated governor P. Hansborough Bell, tried to ramp up military action in defense of the territory against the federal government, but was unsuccessful.[116]
The Latter Day Saint settlers of modern-day Utah had established a provisional State of Deseret, an enormous swath of territory that had little hope of recognition by Congress. The Taylor administration considered combining the California and Utah territories but instead opted to organize the Utah Territory. 