Adjustment of Status – Green Card explained:
Unlike the CR1 Marriage Visa, the beneficiary of a K1 Fiance Visa does not automatically become a Legal Permanent Resident upon entering the United States. Rather, the K1 Fiance Visa is a non immigrant visa that allows the fiance to enter the United States one time for the sole purpose of getting married. The K1 fiance then has 90 days to get married and then must apply for his or her Legal Permanent Residency “Green Card”. The time frame for applying for your Legal Permanent Residency for a K1 Fiance Visa holder is not specially spelled out, other than to say that it must be done soon after the marriage takes place. I think a good rule of thumb is to apply for your Legal Permanent Residency “Green Card” within the first 30-60 days after getting married.
If you have any questions about the K1 Fiance Visa or would like to discuss your immigration plans, you are welcome to call me anytime toll free at 1-888-515-3529.