ABSTRACT. This paper investigates the impact of English speaking ability and age at arrival in the U.S., considered as two major proxies for the degree of social/cultural integration, on occupational achievements of Mexican immigrants in two heavily populated border counties, El Paso (TX) and Pima (AZ). Our various empirical findings point out two major tendencies: first, English fluency appears to be the most important determinant of the position of Mexican immigrants on the occupational ladder. Second, early migration to the U.S. appears to further improve the position of Mexican immigrants in the labor market indicating that there may be components of (cultural) integration/assimilation, which we call "Americanization premium," that are not fully captured by English proficiency alone. Although such premium exists, its magnitude, interestingly, varies between El Paso and Pima. Finally, we will provide a potential explanation for this puzzle.