While in Canada there is only one trademark register, the U.S. has two registers – Principal and Supplemental.
Principal Register
This is the preferable register, as it has several advantages. For example, it gives you trademark protection across the United States, Also, if you do end up in a dispute, the registration itself is the only evidence you need of your exclusive right to use the mark. Your trademark may also be registered with the U. S. Customs Service to block importation of goods bearing an infringing mark.
Supplemental Register
The only requirement for registration on the Supplemental Register is that a mark be capable of distinguishing goods or services, not that it actually do so. It is frequently used for marks that otherwise would be too descriptive for the principal register.
This registration does not confer any additional rights for the mark beyond those provided by common law. Marks registered on the Supplemental Register are not subject to opposition proceedings, but they may be cancelled at any time by a court. Holders of such marks are still permitted to sue for trademark infringement.
There are a number of advantages of Supplemental Register registration over no registration at all. It gives notice of the mark to anyone who searches the USPTO records. It also establishes federal court jurisdiction in an infringement action. In addition the (R) symbol may be used. Finally, such a registration can block registration of a confusingly similar mark to a third party.
After 5 years on the supplemental register, which means at least 5 years of use, one can apply to be registered on the Principal Register by claiming “acquired distinctiveness”.