You will need A VALID PASSPORT.
It is an internationally recognized travel document that verifies the identity and nationality of the bearer. Only the U.S. Department of State and U.S. Embassies and Consulates have the authority to grant issue or verify it.
For travel overseas and to facilitate reentry into the U.S., this document is the best documentation available.
As of June 1 2009, The Western Hemisphere Travel Initiative (WHTI) requires U.S. and Canadian travelers to present a valid passport or other document that denotes identity and citizenship when entering the U.S. It is a result of the Intelligence Reform and Terrorism Prevention Act of 2004 (IRTPA).
The goal of WHTI is to facilitate entry for U.S. citizens and legitimate foreign visitors, while strengthening U.S. border security. Standard documents will enable the Department of Homeland Security to quickly and reliably identify a traveler.
WHTI will go into effect June 1, 2009 for land and sea travel into the U.S. WHTI went into effect for air travelers on January 23, 2007. Official website for extended information or on Travel State Gov.
Some countries require that your passport is valid at least six months or longer beyond the dates of the trip. Contact the embassy of the foreign destination for more information. A listing of foreign embassies and consulates in the U.S. is available on the Department of State’s website.
To view information about entry requirements, check with the foreign embassies or consulates. Contact information can also be found on the Country Specific Information for each country. Check this link and choose the country you’re about to visit.
HOW TO APPLY?
Apply several months before your planned trip, and, if you will need visas from foreign embassies, allow even more time. Even if you don’t have specific travel plans, but have family living abroad or are waiting to find a bargain trip, it is a good idea to apply as early as possible. Information about applying for this.
HOW TO GET IT REPLACED?
If lost or stolen while you are overseas, report it immediately to the local police and to the nearest U.S. Embassy or Consulate. A consul can issue a replacement, often within 24 hours. More information if lost or stolen when abroad.
Contact information for U.S. Embassies and Consulates.
If lost or stolen in the U.S., report it to the Department of State by following instructions.
Source of information: The U.S. State Department.