The Spanish opened Texas to Anglo-American settlers in 1820 to populate the remote region, granting land to those who became Mexican citizens and adopted Catholicism. By 1830, about 20,000 American settlers lived in Texas. However, tensions grew as Mexican laws restricted slavery and required Catholic worship, angering the mostly Protestant settlers. The rise of dictator Santa Anna in 1833 further alarmed Texans, leading to the Texas Revolution for independence.