The Mexican Migration Project began with a simple question: which Mexicans go where in the United States? It seems a simple and obvious inquiry, but it is mostly ignored in the U.S. public discourse. The tremendous heterogeneity of Mexico and the Mexicans, so evident on the ground, is subsumed in analysis that either categorizes all Mexicans as essentially the same — or worse, groups them together with other national-origin groups under the rubric of “Hispanic,” “Latino,” et cetera.