Use as identification and proof of age

Driver's licenses issued in the United States have a number or alphanumeric code issued by the issuing state's Department of Motor Vehicles (or equivalent), usually show a photograph of the bearer, as well as a copy of his or her signature, the address of his or her primary residence, the type or class of license, restrictions and/or endorsements (if any), the physical characteristics of the bearer (such as height, weight, hair color, eye color, and sometimes even skin color), and birth date. No two driver's license numbers issued by a state are alike. Social Security numbers are now prohibited by federal law from appearing on new driver's licenses, due to identity theft concerns. In most states, to be compliant with AAMVA standards, the orientation of a driver's license for person's under the age of 21 is vertical while a driver's license for those over the age of 21 is horizontal. Since the driver's license is often used a proof of a person's age, the difference in orientation makes it easy to determine that a person is legally allowed to purchase or consume alcohol (the drinking age in the US is 21). Most states require that when a driver establishes residence in a state, he or she must obtain a license issued by that state within a certain time frame.

Because there is no national identity card in the United States, the driver's license is often used as the de facto equivalent for completion of many common business and governmental transactions. As a result, driver's licenses are the focus of many kinds of identity theft. Driver's licenses were not always identification cards. Indeed, in many states, driver's licenses did not even have a photograph well into the 1980s. Activism by the Mothers Against Drunk Driving organization for the use of photo ID age verification in conjunction with increasing the drinking age to 21 in order to reduce underage drinking led to photographs being added to all state licenses. New York and Tennessee were the last states to add photos in 1986. However, New Jersey later allowed older drivers to get non-photo licenses; this was later revoked. Vermont license holders have the option of receiving a non-photo license. Later additions varied from state to state, and have included fingerprints, bar codes, magnetic strips, social security numbers and tamper-proof features, most of which were added to prevent identity theft and to curb the use of fake IDs. States have now slowly been converting to digitized driver's licenses, which incorporate holographs and bar codes to prevent forgery.

Non-driver identification cards
All states, usually through the same agency that issues driver's licenses, provide identification cards for people who do not drive. These typically resemble a driver's license and have the same security and identification features. They are commonly used by seniors (who are eligible for free cards in some states), students who choose not to drive, people who are unable to drive, and people in large cities with comprehensive public transportation networks.

Real ID
The Department of Homeland Security has the power through the Real ID Act of 2005 to set standards relating to identification of applicants and license design for state-issued driver licenses and identification cards. States are not required to comply with RealID, but if a state does not comply, any driver licenses or ID cards issued by that state will not be valid for any official purpose with the Federal government, meaning they will not be accepted for entering federal buildings or boarding airplanes.

For a state to meet RealID compliance, licenses and ID cards issued from that state must be approved by DHS in meeting RealID requirements.

States can choose to issue both regular licenses and ID cards as well as RealIDs, but any non-RealID must be marked that it is not a RealID.

RealIDs are only allowed to be issued to legal immigrants and citizens of the United States.

When a person applies for a RealID, either as a new driver license or ID card applicant or renewing a current license or ID card, they must present a citizenship document (US passport, certified birth certificate or citizenship certificate) or proof of legal immigrant status (valid visa) and proof of residency in that state. The state then must verify the documents and store them either electronically or on paper. No one may have more than one RealID at one time.

For those born on or after December 1, 1964, a RealID must be obtained by December 1, 2014 to be allowed to conduct business with the federal government. Those born before December 1, 1964 have until December 1, 2017 to obtain their RealIDs.

Enhanced driver's licenses
Additionally, some states, mostly those with an international border, are issuing Enhanced Driver Licenses and Enhanced ID Cards. Enhanced licenses combine a regular driver's license with the specifications of the new Federal passport card. Thus, in addition to proving driving privileges, the enhanced license also is proof of U.S. citizenship, and can therefore be used to cross the Canadian and Mexican borders by road, rail, or sea, although air travel will always require a traditional passport book due to International Civil Aviation Organization regulations. The enhanced licenses are also fully Real ID compliant.

As of May 2009, Vermont, New York, Michigan and Washington are issuing enhanced driver's licenses and ID cards.

On March 27, 2008, the Secretary of Homeland Security announced that Washington's enhanced driver's license was the first such license approved under the Western Hemisphere Travel Initiative; according to a Homeland Security press release, the department is also working with Arizona authorities to develop enhanced driver's licenses. On September 16, 2008, New York began issuing Enhanced Drivers Licenses that meet WHTI requirements. Texas was expected to also implement an enhanced driver's license program, but the program has been blocked by Texas Gov. Rick Perry, despite a state law authorizing the Texas Department of Public Safety to issue EDLs and a ruling by the state attorney general, Greg Abbott, that Texas' production of EDLs would comply with federal requirements.