What is the U.S. passport card?

On July 14, 2008 the United States started issuing a new travel credential called the U.S. passport card.  The passport card gives residents of Texas, Vermont, Washington, Michigan and other border states a less expensive and more portable alternative to the traditional passport book.  The card has the same period of validity as a passport book: 10 years for an adult, five for children 15 and younger.  Adults who already have a fully valid passport book may apply for the card as a passport renewal and pay only $20.  First-time applicants pay $45 for adult cards and $35 for children.  This is less than half the cost of a U.S. passport book.