They moved to Texas because the Mexican government offered large tracts of free land to the settlers. Mexico banned settlers in the 1830's because American settlers ignored Mexican laws. Mexico felt like it was losing control over the growing American population, so they banned further settlement.
How and why did Texas attract American settlers? Stephen Austin was given land to offer to them; settlers wanted land for farming and ranching. They sent troops to Texas, battled the Texans, then signed a treaty giving Texas independence.
The settlers demanded greater representation and more power from the Mexican Government. Revolts broke out in 1832 and 1833. Instead, General Santa Anna, dissolved the national congress late in 1834, and became dictator in Mexico. In Texas, American settlers decided to promote their own independence from Mexico.
Because they could be turned into slave states, giving more power to the slave owners in the south. Also, expansion policy and the dram of Manifest Destiny played a part in desiring that land.
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