For those who chose to seek US citizenship, it is the last leg of their personal journey.  Not only does it allow one to vote, apply for certain federal jobs and carry a US passport, one can also apply for green cards for parents, married children, brothers and sisters, and allows for faster immigration for spouses, children under 21.  In certain instances, naturalization of a parent can result in automatic citizenship for children under 18 years of age, who hold green cards at the time the parent is naturalized.  The process requires the filing of an application, fingerprints and an interview at USCIS.  During the interview, one must demonstrate knowledge of English and pass a civics test (certain older applicants are exempted from the English and civics exams.)