Unlike many other countries, the United States has what is called a first-to-use trademark system. That means that the first entity to use the mark within a territory acquires a right of priority to use that mark over all subsequent users in that location. Under common law, the first user (a.k.a. “senior user”) has superior rights to use a mark within a territory, regardless whether or not it has been federally registered with the U.S. Patent & Trademark Office (“USPTO”). In fact, if a subsequent junior user registers an identical or similar mark with the USPTO, the prior senior user still has exclusive priority to use the mark in its territory as well as its zone of natural expansion. Nowadays, when it is very common to sell products and services over the Internet, that territory could be large and thus extensively limit the use of the junior user’s mark, even if it has been federally registered.
Overall, there are many dangers that accompany the use of a trademark without properly conducting a comprehensive trademark search. Too many companies invest heavily in developing, branding, promoting, and advertising a product or service with a certain trademark, only to find out that they may be prevented in even using the mark altogether. To avoid costly legal disputes that may result in a company being forced to stop using its mark, it is best to consult with an experienced trademark attorney and have him or her perform a comprehensive trademark search before using a mark.