Mexico Mexico, in full United Mexican States (Spanish Estados Unidos Mexicanos), federal republic in North America, bounded on the north by the United States; on the east by the United States, the Gulf of Mexico, and the Caribbean Sea; on the south by Belize and Guatemala; and on the west by the Pacific Ocean. Mexican federal jurisdiction extends, in addition to Mexico proper, over a number of offshore islands. The area of the country is 1,958,201 sq km (756,066 sq mi). The capital and largest city is Mexico City. Most of Mexico is an immense, elevated plateau, flanked by mountain ranges that fall sharply off to narrow coastal plains in the west and east. The two mountain chains, the Sierra Madr