How can noncitizens acquire citizenship in this country?

Noncitizens can acquire citizenship in the United States primarily through the naturalization process. This typically requires them to be lawful permanent residents (green card holders) for a certain period, usually five years, or three years if married to a U.S. citizen. Applicants must demonstrate good moral character, pass English and civics tests, and fulfill other requirements. Additionally, some noncitizens may obtain citizenship through other avenues, such as military service or through parents who are U.S. citizens.