Many people are unaware of this fact but the United States Patent and Trademark Office (USPTO) has a roster of all US patent attorneys and agents. The searchable roster can be found here. Since I am a patent attorney, my information is listed on the roster and can be found here. Only people who have passed the patent bar and background check, and graduated from an accredited law school and passed a state bar exam can be listed as a patent attorney on the USPTO roster. Patent agents need only to have passed the patent bar and background check–law school and state bar are not required for patent agents.
The USPTO roster of patent attorneys is a valuable tool for inventors to make sure the “patent attorney” or “patent agent” they are dealing with is a patent practitioner in good standing and who has achieved all the requirements necessary to be a patent practitioner. You can search the roster, name, state, city, postal code, and business or firm name.
Unfortunately, the USPTO does not have a roster of all trademark attorneys.