The U.S. Patent and Trademark Office (USPTO) maintains a list of all registered trademarks.  The USPTO list includes the “Principal Register.” When a trademark is listed on the ‘Principal Register’, it puts all parties in the country on constructive notice of the registration as well as the registrant’s use of the mark. When a mark has been included on the ‘Principal Register’, the owner of that mark is entitled to exercise all of the rights provided by the U.S. Trademark Act.