Saturday is the U.S. State Department's national "Passport Day in the USA 2012," a national passport acceptance and outreach event.
The Post Office will be accepting passport applications and providing information to U.S. citizens.
Federal law requires U.S. citizens to present a valid passport book when entering or re-entering the United States by air.
U.S. citizens entering the United States from Canada, Mexico, the Caribbean and Bermuda - at land borders and sea ports of entry - must present a passport book, passport card or other travel documents that have been approved by the U.S. government.
Application requirements and fees vary, based on age and whether the person is applying for a first passport or a renewal.
Information on the costs, and on applying for a U.S. passport, is available at the State Department's website, travel.state.gov.
U.S. citizens also may also obtain passport information by phone, in English and Spanish, by calling the National Passport Information Center toll-free at 1-877-487-2778.