The letters appeared above one of the entrances to the historic building, which is located just a few blocks from the White House.
Other images emerged on social media showed a projection of the emoluments clause of the US constitution, which prohibits federal officials from taking payments from foreign governments.
The clause reads: “No title of nobility shall be granted by the United States: And no person holding any office of profit or trust under them, shall, without the consent of The Congress, accept of any present, emolument, office, or title, of any kind whatever, from any King, Prince, or Foreign State.”
President Trump faces a lawsuit, filed by ethics watchdog group Citizens for Responsibility and Ethics in Washington, that alleges he violated the emoluments clause.
The lawsuit suggest Mr Trump is violating the US Constitution by accepting payments from foreign governments through his hotel.
Social media users were quick to react to images of the projected images.
One user wrote: “This should never stop. Can this be done on the White House?”
Another tweeted: “Made my night! So good. Hats off to the projectionist displaying the truth on Trump’s DC property! He will have a meltdown.”
The news comes just hours after President Trump reportedly revealed highly classified information about ISIS to the Russian foreign minister Sergey Lavrov during a White House meeting last week.
A US official claims the President “revealed more information to the Russian ambassador than we have shared with our own allies”.
The President is alleged to have gone off script and began describing details about an ISIS threat related to the use of laptop computers on aircrafts.
He is also alleged to have boasted to Russian diplomats about the intelligence he regularly receives and may have risked the future relationship with the important source.
Mr Trump reportedly said: “I get great intel. I have people brief me on great intel every day.”
Top White House staffers, including Secretary of State Rex Tillerson and US national security advisor H.R. McMaster, have defended the President and said the allegations are false.