If you are traveling in the Western Hemisphere (Canada, Mexico, Caribbean, Central and South America):
Air Travel: All U.S. citizens departing from or entering the United States from within the Western Hemisphere by air are required to present a valid passport or NEXUS card (if utilizing a NEXUS kiosk when departing from a designated Canadian airport). Merchant Mariner Document (for U.S. citizens on official maritime business.) U.S. Military identification card when traveling on official orders; Note that children are also required to present their own passport when traveling by air.
Land or Sea Travel: U.S. citizens entering the United States by land or sea are required to present a valid WHTI-compliant document, which include:
U.S. Passport Cards
Enhanced Driver's Licenses
Trusted Traveler Cards (Global Entry*, NEXUS, SENTRI, or FAST)
Military Identification Cards (for members of the U.S. armed forces on official orders)
U.S. Merchant Mariner Document (for U.S. citizens on official maritime business)
*The Global Entry (GE) card is only an ENTRY document and may not be used to enter Canada, Mexico or Adjacent Island.
Military personnel traveling under orders may present photo ID and orders. Family members must present a passport (with the exception of children 15 and younger arriving by land or sea.)
Children: U.S. citizen children ages 15 and under arriving by land or sea from a contiguous territory may present an original orcopy of his or her birth certificate (issued by the Vital Records Department in the state where he or she was born), a Consular Report of Birth Abroad, or a Naturalization Certificate. If the child is a newborn and the actual birth certificate has not arrived from the Vital Records Department, the center will accept a Hospital issued birth certificate.
Groups of Children: U.S. citizen children between the ages of 16-18 arriving by land or sea from contiguous territory and traveling with an adult supervised school group, religious group, social or cultural organization, or sports team, may also present an original or copy of his or her birth certificate, a Consular Report of Birth Abroad, or a Naturalization Certificate.
For documentation requirements regarding cruises see Frequently Asked Question "What Documents do I need for Cruises"