Registration with the U.S. Patent and Trademark Office, on the other hand, provides nationwide trademark rights to the first user. If, for example, a federally registered mark conflicts with a mark which is unregistered, the owner of the unregistered mark does not have trademark rights outside of the owner's geographical market, even if the unregistered mark was in use prior to the registered mark. 

There are thus two factors to be considered when evaluating trademark rights: use and registration. And (until recently) even when considering registration alone, actual use in interstate commerce was required before an application for registration could be filed. It is now possible, however,to file an application to register a trademark or service mark without actual use, provided there is a bona fide intent to use the mark with respect to a product or service in the immediate future, and the mark is subsequently so used before registration.

To summarize, if you have been using a trademark for a period of time in a given area, no one else used it before you in that area, and there was no existing federal trademark registration in effect or applied for at the time you started using the mark, you already have certain trademark rights in that geographical area. If someone else is using the mark in another geographical area (and you have not) and you apply for federal registration, you may not prevent their use of that mark in that area (if it pre-dates yours) even if you secure a trademark registration. But if you secure trademark registration (and the other user does not), you will ordinarily have superior rights to the trademark in geographical areas which are new to you and the other user as well.