One of the most important documents in the United States is the social security card. If you don’t plan to drive while you’re here, it is the main form of identification. We use our social security number (SSN) for our financial documents, legal forms, and medical forms. You need one to work in the United States, conduct business with a bank, and to pay your taxes.
Because of the importance of a social security number, it is easier if you apply for your social security card before you arrive in the U.S., as part of your visa application process. However, if you are not able to do that, getting a social security card will be one of the first tasks on your list after you arrive.
Excerpt from “10 Things You Need to Know: A Practical Guide for Internationals Moving to the U.S.” www.10thingsyouneedtoknow.info