The letter, sent to the U.S. Department of Justice's Deputy Attorney General Rod Rosenstein, calls the firing of FBI Director James Comey during his ongoing investigation "a violation of the public trust."
"As prosecutors committed to the rule of law, we urge you to consider the damage to our democratic system of any attempts by the administration to derail and delegitimize the investigation," the letter states.
The attorneys general also argue that the residents in their states "deserve a thorough investigation that makes clear the extent of Russian meddling, any collusion by Trump campaign officials, and any cover-up."
Click here to read the letter.
The letter was signed by the attorneys general from Massachusetts, California, Connecticut, Delaware, the District of Columbia, Hawaii, Iowa, Illinois, Maine, Maryland, Minnesota, New Mexico, New York, North Carolina, Oregon, Pennsylvania, Rhode Island, Virginia, Vermont and Washington.