US expansion was complicated by the division between "free" and "slave" states, which led to the Missouri Compromise 1820. Likewise, Canada faced a division between French and English communities that led to the outbreak of civil strife in 1837. Mexico faced constant political tensions between liberals and conservatives, as well as the rebellion of the English-speaking region of Tejas, which declared itself the Republic of Texas 1836. In 1845 Texas joined the United States, which would later lead to the Mexican–American War. As a result of conflict with Mexico, the United States made further territorial gains in California and the Southwest.