How do you find out the last registered owner of an ATV?

Depending on what state you live in....you must file the paperwork with the issuing authority.

Here in Pa the DCNR will check to see if there ever was a title holder then send notice that you are attempting to title it and investigate as to why the title was never transferred.

If the original title owner does not reply, a new title in your name will be issued.

But again, each state may be different