In 1835, American settlers in Texas revolted against Mexico and won their independence. Most people of the time assumed that at some point Texas would be annexed to the United States and later subdivided into a number of territories that would eventually become states.
Andrew Jackson wanted Texas to join the Union, but realized that the admission of one or more slave states would upset the sectional balance so carefully guarded since the Missouri Compromise. Desiring to avoid controversy, Jackson waited until his final day in office before formally recognizing Texas independence, a step closer to statehood. This action was also a favor to his successor, Martin Van Buren, who would not have to handle that hot potato.