Most are called bureaus or departments of motor vehicles. The driver's licenses from the fifty states all look different, some with photos, some produced like credit cards. A driver's license from any one state is valid in every other state. There is no national identity card in the United States, and the individual state driver's license is the most respected and widely used form of personal identification. To obtain a driver's license, you must first locate the state agency responsible.
Most telephone books have special sections for government offices.
Or ask any policeman. Expect a vision test, and perhaps a required class in safety. You might have to be photographed. Finally you will take an actual road test with an examiner in an automobile. The Driving Test.