If you are 17 years old and an illegal alien in the US how do you become a legal citizen without marrying a legal US citizen?

You can be adopted by a US citizen. You can be sponsored by an immediate relative that is a US citizen or a permanent green card holder. Marrying a U.S. citizen does not automatically confer citizenship or permanent resident status on the new spouse. Adoption is only allowed if the child is 16-years or younger has been certified an orphan by his or her country of origin and has been granted an IR4 visa for entrance into the United States. Contact the United States Citizenship and Immigration Services for information pertaining to the individual's specific circumstances or visit http://www.uscis.gov