As of June 1, 2009 both the Canadian and US Government have changed your requirement documents to cross the border by land. A list of the acceptable documents are listed below and if you require more information you can go to http://www.getyouhome.gov/html/eng_map.html.
U.S. Passport – This is an internationally recognized travel document that verifies a person’s identity and nationality. It is accepted for travel by air, land and sea.
U.S. Passport Card – This is a new, limited-use travel document that fits in your wallet and costs less than a U.S. Passport. It is only valid for travel by land and sea.
Enhanced Driver’s License (EDL) – Several states and Canadian provinces/territories are issuing this driver’s license or identification document that denotes identity and citizenship. It is specifically designed for cross-border travel into the U.S. by land or sea.
Trusted Traveler Program Cards – NEXUS, SENTRI or FAST enrollment cards can speed your entry into the U.S. and are issued only to pre-approved, low-risk travelers. The cards are valid for use at land or sea; the NEXUS card can be used in airports with a NEXUS kiosk.