|"Is this all real? Or has this been happening inside my head?"
The topic of this article is of a real-life subject that has been mentioned "in-universe" in a canon source. The Harry Potter Wiki is written from the perspective that all information presented in canon is true (e.g., Hogwarts really exists), and, as such, details contained in this article may differ from real world facts.
The Continental Congress (known by wizards of the time as the No-Maj Congress) was the governing body of the No-Maj population of the United States of America during the Revolutionary War. When Congress established their headquarters in Baltimore at the start of the Revolutionary War, the Magical Congress of the United States of America, which was also headquartered in the city at the time, decided to relocate to Washington.