Just for clarification for people who will see this in the future as there is some nuance, IF YOU LOST YOUR GREEN CARD (like I did) then you decide to apply for the N400, you still need to file for the replacement of the Green Card. 20 years as an LPR...brother, why? You will need to document every traffic ticket, police contact, every job you have had, every place you have lived or moved to, and whether you notified USCIS timely, travel in/out the country etc. Really discourage folks living in LPR status for so long....as the N400 application can bury you.