As southern agriculture expanded westward, some whites looked toward Texas for fresh land. White Southerners had begun moving into eastern Texas in the early nineteenth century, but the Adams-Onís Treaty of 1819 guaranteed Spanish control of the territory. Then in 1821 Mexicans overthrew Spanish rule and claimed Texas as part of the new Republic of Mexico. But Mexicans faced serious competition from Comanche Indians, who controlled vast areas in northern Mexico and launched frequent raids into Texas.

Eager to increase settlement in the area and to create a buffer against the Comanches, the Mexican government granted U.S. migrants some of the best land in eastern Texas. It hoped these settlers would eventually spread into the interior, where Comanche raids had devastated Mexican communities. To entice more Southerners, the Mexican government negotiated a special exemption for U.S. planters when it outlawed slavery in 1829. But rather than spreading into the interior, American migrants stayed east of the Colorado River, out of reach of Comanche raids and close to U.S. markets in Louisiana.

Moreover, U.S. settlers resisted assimilation into Mexican society. Instead, they continued to worship as Protestants, speak English, send their children to separate schools, and trade mainly with the United States. By 1835 the 27,000 white Southerners and their 3,000 slaves far outnumbered the 3,000 Mexicans living in eastern Texas.

Forming a majority of the east Texas population and eager to expand their plantations and trade networks, growing numbers of U.S. settlers demanded independence. Then in 1836 Mexicans elected a strong nationalist leader, General Antonio López de Santa Anna, as president. He sought to calm Tejanos (Mexican Texans) angered by their vulnerability to Comanche attacks and to curb U.S. settlers seeking further concessions. However, when Santa Anna appointed a military commander to rule Texas, U.S. migrants organized a rebellion and, on March 2, declared their independence. Some elite Tejanos, long neglected by authorities in Mexico City, sided with the rebels. But the rebellion appeared to be short-lived. On March 6, 1836, General Santa Anna crushed settlers defending the Alamo in San Antonio. Soon thereafter, he captured the U.S. settlement at Goliad.

At this point, Santa Anna was convinced that the uprising was over. But the U.S. government, despite its claims of neutrality, aided the rebels with funds and army officers. American newspapers picked up the story of the Alamo and published accounts of the battle, describing the Mexican fighters as brutal butchers bent on saving Texas for the pope. These stories, though more fable than fact, increased popular support for the war at a time when many Americans were increasingly hostile to Catholic immigrants in the United States.

As hundreds of armed volunteers headed to Texas, General Sam Houston led rebel forces in a critical victory at San Jacinto in April 1836. While the Mexican government refused to recognize rebel claims, it did not try to regain the lost territory. Few of the U.S. volunteers arrived in time to participate in the fighting, but some settled in the newly liberated region. The Comanche nation quickly recognized the Republic of Texas and developed trade relations with residents to gain access to the vast U.S. market. Still, Santa Anna’s failure to recognize Texas independence kept the U.S. government from granting the territory statehood for fear it would lead to war with Mexico.

President Jackson also worried that admitting a new slave state might split the national Democratic Party before the fall elections. To limit debate on the issue, Congress passed a gag rule in March 1836 that tabled all antislavery petitions without being read. Nevertheless, thousands of antislavery activists still flooded the House of Representatives with petitions opposing the annexation of Texas.