To become a naturalized u.s. citizen an alien must have lived in the u.s. for how long?

If your legal resident status was obtained through marriage to a US citizen, you can apply for citizenship as early as 2 years and 9 months after you were granted permanent residency. If your legal resident status was obtained through means other than marriage to a US citizen, you may apply as early as 4 years and 9 months after you were granted permanent residency. Once you apply, it takes between 6 and 9 months to process.