With the Treaty of Guadalupe Hidalgo in 1848, Hispano settlers, or pobladores, of the San Luis Valley became Americans overnight. The pobladores of the large land grants were legally granted citizenship of the United States, and their property rights were to be recognized. Most did not speak English or understand the United States government or culture, and they were unaware that their land was being bought and sold with the stroke of a pen in places as distant as New York and Holland. When pioneering Americans from the East came to the San Luis Valley to claim land, they found thriving Hispano communities already there. Unable to prove ownership of their land, many pobladores were treated as squatters, ejected, and forced to buy their land back. The valley became the focus of hundred thousand acre land disputes, and by the early 1900s millions of acres of former land-grant territories in the San Luis Valley had changed hands. Despite this, Hispano culture survived and thrived in the valley's isolation.