If you have resided continuously in the U.S. since before Jan. 1, 1972 you can apply under a special program known as Registry
You can read our entire series, "Who Gets A Green Card?" below:
Who Gets A Green Card? : Through a Job or Job Offer
Who Gets a Green Card?: Special Immigrants
Who Gets A Green Card? : People Granted Political Asylum and Refugees
Who Gets a Green Card?: Trafficking and Crime Victims
Who Gets A Green Card?: Victims of Abuse
Who Gets A Green Card?: Those Residing Here Since 1972
Who Gets A Green Card?: Various Other Categories