1 Location and Size. Coahuila, in northern Mexico, is one of the three largest states in Mexico. It has an area of 149,511 square kilometers (57,726 square miles), about the same size as the US state of Michigan.oahuila is bordered on the north by the US state of Texas; on the east by the Mexican state of Nuevo Leon; león on the south by The mexican states Of, Zacatecas, durango And San Luis; potosi potosí and on the west By the mexican State. of chihuahua