The history of Mexican-American people is wide-ranging, spanning more than four hundred years and varying from region to region within the United States. Mexican-Americans were once concentrated in the states that formerly belonged to Mexico, including California, Arizona, New Mexico, Colorado and Texas; they began creating communities in Los Angeles, Santa Ana, California, San Francisco, Denver, Houston, San Antonio, Texas and other steel producing regions when they obtained employment there during World War I. More recently, Mexican immigrants have increasingly become a large part of the workforce in industries such as meat packing throughout the Midwest, in agriculture in the southeastern United States, and in the construction, landscaping, restaurant, hotel and other service industries throughout the country. Mexican-American identity has also changed markedly throughout these years. in past hundred years Mexican-Americans have campaigned for voting rights, stood against educational, employment, ethnic discrimination and stood for economic and social advancement.