How do I know if I am legally eligible for employment in the United States?

First job application, and I am not sure what is required to be legally eligible for employment in the U.S.

How do I know if I am legally eligible for employment in the United States?
Most apps will ask you to provide a SS number, which you should have if you are a citizen, or an alien residence number, which you should have if you got here legally. To answer your question, you just have to be a LEGAL resident of the country or have a work VISA. If you jumped a fence to get here, then you should go back home because breaking the law is wrong!
Reply:Go to the web site http://www.uscis.gov/files/form/i-9.pdf it lists the documents necessary to prove authorization to work in the U.S. that you will need to present in order to be hired by an employer. "All employees, citizens andnoncitizens, hired after November 6, 1986, must complete Section 1of this form at the time of hire, which is the actual beginning of employment."