For thousands of years before the existence of the nations of Mexico and the United States, Native people called the border between these two modern nations home. This map shows the many Tribal Nations and cultural groups whose lands were divided as a result of the Mexican-American War ( or in Spanish : "La Invasíon Americana") and the Treaty of Guadalupe Hidalgo. Today, most of these Tribes still have descendants on both sides of the border. Some have special permits to cross back and forth to visit relatives and sacred places. Most do not.