One path of many to become an American citizen is to marry an American citizen inside of the United States using the K-1 Visa. For many, this is a necessary step in ensuring that a non-American citizen and American citizen can live together in the same country. According to the US State Department, if you are the recipient of a K-1 Visa, you must marry the American citizen within 90 days of arriving in the United States.
In some situations it is not necessary to obtain a K-1 Visa in order to marry in the United States. The main benefit of the K-1 Visa is that it allows the recipient to easily transition over to a Green Card after the marriage has gone through legal channels. However, for example, if the non-American citizen is from a country that is eligible for the ESTA visa waiver, it is technically possible for the non-American citizen to marry the American citizen within the United States. It is also technically possible if the non-American citizen is inside of the United States with a student visa or a work visa.
The problem with this approach is that getting married on an ESTA visa waiver (or a student or work visa) is considered getting married in “bad faith” in most circumstances because this is a way of circumnavigating the K-1 Visa process. If this is the case, it can be very difficult for the non-American citizen to obtain a Green Card.
If you are looking to obtain a Green Card for the non-American citizen of a marriage, it is important to go through the K-1 Visa process for the least amount of stress.