Most personal information is protected closely by police and the motor vehicle departments in each state, so it can be difficult to find a person using a number plate number. If you got a good look at the number plate, write down all the details you can as soon as possible including the number, the state and whether the number plate had a special design. These details can help you track the plate's owner.
Stop at your local motor vehicle department and look at the styles of personalised plates. Some are linked to specific organisations or causes. If the number plate you are looking for was personalised, contact the organisation to explain why you are attempting to find the person. Give the organisation the number plate number you have. Someone may be able to assist you.
Buy a membership in a website that offers private investigator search tools. While costs may go as high as £65, you can access databases that you would not be able to browse otherwise, and doing the legwork yourself will be cheaper than hiring a private investigator to perform the same searches for you.
Use services such as Abika and DocuSearch Investigations. For a fee, you can access names of people based on number plate numbers. You should check to be sure the state you are looking for is supported before you pay the fee.
Take the information you have to the motor vehicle department and request the name of the person. Once you have the name, you will be able to find the individual more easily although the department cannot give out any additional contact information. This isn't possible in every state, as some states have laws that protect the privacy of their inhabitants.