Starting in the 1800s, the Spanish colonized the Navajo territory as part of Mexico. Then the US took over the area after the Mexican-American war. After that, American settlers came and set up schools to teach the Navajo about English and Christianity. They did not allow the Navajo to use their language in order to make them learn English. Children were forced to wash out their mouths with soap if teachers found them speaking Navajo. Because of this, many parents were afraid to teach their children the language.