In 1848, the Treaty of Guadalupe Hidalgo, which succeeded Mexico’s claim of today’s western US, did not automatically transfer ownership of all land. In fact, the treaty gave about 100,000 people living on Mexican land the ability to become United States citizens by just deciding so. The landowners would also be able to keep any property grants which were already in place should they stay or return to Mexico. The US was to honor private property granted by either Mexico or Spain who had been in control of the area for over 250 years.
Yet, what was agreed upon and what actually happened are two different situations. In some places, Mexican, Spanish, and indigenous people were stripped of their land immediately. Some residents with valid land grants were not recognized by the new officials at all. They demanded land documentation be in English, even though Spanish had been the regional language for centuries. If landowners couldn’t afford the new documentation, their land was taken away.
In other situations, Anglo Texans used their connections in Austin to shape state law or use law enforcement for their own personal benefit. In a few cases, violent mobs would simply assault or torment landowners, coercing them to leave –– knowing they were unaware of their rights.