Travelers snapping up cards for border trips

The State Department's new passport cards, which are wallet-sized identification cards designed to speed border crossings by U.S. citizens to Canada, Mexico and the Caribbean, are proving popular already.

More than 350,000 Americans have pre-ordered the passport cards, according to the State Department.

The card is not valid for any type of air travel. It can only be used for land and sea crossings between the U.S. and Canada, Mexico, Bermuda or the Caribbean.