San Francisco Public Library
Español中文

Common Law Trademark Sources

What are trademarks?

According to the U.S. Patent and Trademark Office, a trademark is a "word, phrase, symbol or design, or a combination of words, phrases, symbols or designs, that identifies and distinguishes the source of the goods of one party from those of others."

What is the difference between registered trademarks and unregistered trademarks?

Some trademark owners register their marks with the U.S. Patent & Trademark Office. Registered trademarks are indicated by the symbol "®" and allow certain rights in interstate and foreign commerce.

The first business to use a trademark generally obtains certain common law rights to it, whether or not it is registered. The owners of unregistered trademarks may indicate their claim to common law rights to the trademark by using "TM" with it.

Of course, the United States Patent and Trademark Office’s Web site has official information about trademarks. San Francisco Public Library has a Patent and Trademark Center and a Patent and Trademark librarian whom you may contact. The Patent and Trademark Center offers occasional classes on patent and trademark topics.

What is a common law trademark search?

A common law trademark search involves checking directories, databases and other sources to see whether a given trademark has been used already, meaning someone may have common law rights to it.

A common law trademark search is generally done as a last step after searching for registered federal trademarks using TESS (Trademark Electronic Search System) and also after searching for registered individual state trademarks. (Contact the Patent and Trademark Center for more info about searching for registered trademarks.)

Why is it a good idea to do a "common law" trademark search on the name I want to use for my company / product / service / band?

If you want to register your trademark, the federal trademark application requires a signed declaration from the applicant that "to the best of his/her knowledge and belief no other person, firm, corporation, or association has the right to use the mark in commerce…"

Legal considerations aside, it is good business sense to create a unique name and/or logo that identifies your product or service and that you won’t have to change later.


What are some sources I can check at San Francisco Public Library?

Following is a list of some of the major sources one can consult in doing a common law trademark search.

Databases listed below may be accessed through the Library’s web site using a library card number and a PIN. Unless noted otherwise, all print sources are located in the Business, Science & Technology Center.

General Sources of Business Names

A business name is not in itself a trademark. But it is still useful to search general business directories to find out what names are in use.

California Businesses

California Business Search - access to millions of records filed in the State of California's databases for CA corporations (including nonprofits), limited partnerships (LP) and limited liability companies (LLC). Also try the Name Availability searches.

Fictitious Business Name (FBN) Search

The law requires every person who transacts a business for profit under a fictitious business name (FBN) to file a statement in the county of the principal place of business within 40 days from the time such business commences. The statement expires in 5 years and a new filing is required upon expiration. Fictitious Business Name Statements are required to ensure that consumers have access to the true name and address of the owners of a business. For local (SF) businesses, use San Francisco Fictitious Business Name Search.

Print Directories of Local Businesses

[See Local Company Research Resources for a more complete list of local sources]

General Sources of Brand & Product Names

Sources for Specific Goods & Services

The Business, Science & Technology Center has many print trade directories for a wide range of industries. 

Additional Suggestions