In most cases, an applicant for citizenship must have been a lawful permanent resident continuously resident in the United States for five years immediately preceding the application.
Where lawful permanent residence was obtained through marriage to a US citizen, only three years of continuous residence immediately preceding the application is required. An absence of six months or more breaks the continuous residence requirement unless the applicant has a reasonable explanation for the absence. In addition to the continuous residence requirement, the applicant for citizenship must be physically present in the United States for half of the five or three year continuous residence requirement. The applicant must be resident for at least three months in the state in which the petition is filed and must be able to speak, read and write ordinary English.
At the citizenship interview, the applicant will be required to take a short test on the history and political system of the United States. The test may be waived for medical reasons. All citizenship applicants must present proof of having filed tax returns.
Current processing times on the East Coast are 12-18 months from time of filing.