According to the Mexican embassy, American citizens do not need a passport to enter Mexico. But they must show a government photo ID such as a driver's license.
The U.S. State Department declares that Americans need a passport or passport card to re-enter the United States when traveling by land, sea or air.
U.S. citizens do not need a visa or tourist card if staying 72 hours or less within the border zone, which is 20 to 30 kilometers from the U.S. border.
Those wanting to stay longer, travel farther in or enter Mexico by air require a tourist card, which is easily obtained from the Mexican consulates, border crossings, tourism offices and airline companies.
Those traveling beyond the border zone with cars need a temporary import permit or their vehicles can be confiscated by customs.
