Learner's permits are granted by some states to drivers as young as fourteen. Some states also issue driver's licenses to 14 or 15 year old drivers to drive alone. New Jersey issues licenses to 17 year olds and in New York City, senior licenses may be obtained only by 18 year olds or 17 year olds who have completed a driver's education course.

In all of these states, the laws which apply are those of the state in which the driver operates the motor vehicle. (Example: a 14 year-old learner's permit holder in Arkansas would have to wait until 14½ to drive in Montana, or a 16 year-old driver's license holder from West Virginia must follow all learner's permit standards for driving in Pennsylvania until he or she turns 16½).

Many states share a common system of license classes, with some exceptions, and commercial license classes are standardized by federal law:

Commercial Driver's Licenses (CDL)
Class A: Combination vehicle of 26,000 lb (11,790 kg) or more
Class B: Single (straight) vehicle of 26,000 lb (11,790 kg) or more (also includes most buses)
Class C: Commercial vehicle that doesn't fit classes A or B, but is placarded for hazardous materials or is intended to carry 14 passengers or more (excluding Georgia)

Standard Qualified Driver's Licenses
Class D: Passenger vehicle (although this category is universal, the actual title varies by state: for example, Mississippi calls this Class R, while Texas calls it Non Commercial Class C, Georgia calls this Class C, Florida calls this Class E and Hawaii calls it Class 4)
Class E: Taxi Driver or Chauffeur. Taxi driver licensing in the United States is somewhat complicated. A Class E (or similar) license is issued by the state department or agency with the power to issue driver's licenses. Not all state licensing boards (such as Massachusetts) require or issue a chauffeur license. However, regardless of whether a license is required at the state level or not, a license or permit must be obtained from local authorities to operate a taxi, usually the city or county one wishes to drive in. This is separate to and must be obtained in addition to any license required at the state level.
Class M: Motorcycle-{excluding any motorcycle 50 cc and under} (unlike in Europe, the United States does not differentiate between low and full powered motorcycles for the purposes of licensing)

Some states also have additional classifications. Hawaii, for example has a separate license category for drivers who only operate mopeds. South Carolina has non-commercial versions of every commercial class license.

Commercial Driver's License Endorsements
Professional drivers are usually required to add endorsements to their CDL in order to drive certain types of vehicles that require additional training, such as those equipped with air brakes. CDL endorsements are also common among all states, and the training and testing requirements are regulated by the Federal Government. Endorsements are as follows:
P: Passenger Transport (Required to drive a bus that carries 14 people or more)
H: Hazardous Materials (Also requires a TSA criminal background check as well as a written exam. You must be a US Citizen to obtain an H or X endorsement.)
N: Tank Vehicles, Required for carrying liquids in bulk
T: Double/ Triple Trailers (Road trains) (Class A licenses only)
X: Hazardous Materials and Tank Combination
L: Air Brakes
S: School Bus (Also requires a TSA criminal background check, a sex offender registry check, and a "P" endorsement.)

In the U.S., minimum driving ages vary from state to state ranging from 14 to 18. Some examples are below. The minimum age for a Commercial Driver's License is typically 21, except for school bus drivers, which is sometimes as high as 25, although some individual states permit drivers who are 18 to apply for a non HazMat, non school bus intrastate only CDL.

Driver's license information by state

Decline in licensing among young people in the U.S.
In the past decade, fewer and fewer teenagers are getting driver's licenses. According to a December 2, 2004 Los Angeles Times article, only 43% of American 15-, 16-, and 17-year olds had licenses in 2002.[10] By comparison, the percentage in 1982 was 52%. The rate is even lower in some states (e.g., 9% in Missouri). The decrease in percentages are said to be due to the many restrictions that an average teen must face overall in order to obtain the licenses.

For example, in Pennsylvania, when drivers under the age of 18 obtain a permit, they must hold that permit for 6 months, and must have completed at least 50 hours of behind-the-wheel training with a driver licensed in Pennsylvania that is at least 21 years of age. After meeting this requirement, drivers can attempt the supervised driving test. After passing the driving test, newly licensed drivers under 18 must be accompanied and supervised by a licensed parent, guardian or other licensed driver 25 years of age or older or a licensed or certified driving instructor when they:

Drive between 11pm and 5am for the first twelve months unless they have notarized proof of employment or volunteer work during that timeframe.

After obtaining his or her license, the individual may transport as many passengers as there are seat belts in the vehicle. Must be accompanied and supervised by a licensed driver when they:

Drive between 2am and 5am for the next six months.
Instead of facing these provisions, many drivers under the age of eighteen today simply wait until they turn eighteen to get their driver's license in order to bypass these restrictions.

Other information and use as identification
Most U.S. states require new drivers to complete both driver's education classes (which include both classroom lectures and textbook lessons) and driver training (behind the wheel lessons with a state-licensed driving instructor) in order to earn a driver's license.

U.S. driver's licenses have a unique number or alphanumeric code issued by the 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, and sometimes even skin color), and birth date. Social Security numbers are becoming less common on driver's licenses, due to identity theft concerns. In some states the orientation of a provisional driver's license (for those under the age of 21) is vertical while a regular driver's license (for those over the age of 21) is horizontal. 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.

In the case that a person lacks a driver's license, due to license suspension or being a non-driver, a state identification card (state ID) can be issued by the DMV in its place.