The Tyler and Polk administrations
Both administrations strongly supported American westward expansion.
John Tyler pressed for the annexation of Texas as a slave state during his administration (1841-45) and at the end of it, he signed a Texas annexation bill into law, which was admitted as a state in the first year of Polk's presidency.
James K. Polk, who ruled from 1845 to 1849, also supported American expansion to the point he led the U.S. into the Mexican-American War (1846-48) in which the U.S. gained what is today California and much of the present-day Southwest.
