First-time passport for an adult who has never claimed U.S. citizenship before

The requirements for transmitting citizenship depend on whether the parents were married at the time of birth, which parent is a U.S. citizen, and how long the U.S. citizen parent spent in the U.S. before the child’s birth.  To apply for a first time adult passport, both the applicant and his/her U.S. citizen parent must appear in person at the Embassy for the appointment.

Instructions for first-time adult passport, never documented as a U.S. citizen before