The rebellion was blamed on Irene Kneedander, Head of the Body for the Protection of Magical Species.Kneedander had taken to attacking a Sasquatch that had done something wrong which led to their decision to rebel. They needed a new headquarters, and over the course of several years, wizards infiltrated the construction team of a new building in New York.
Due to the indiscretions of the dim-witted witch Dorcus Twelvetrees, the then President Emily Rappaport created Rappaport's Law, which would enforce strict segregation between the No-Maj and wizarding communities.
Henceforth, wizards were no longer allowed to befriend or marry No-Majs, and penalties of such fraternisation were harsh.
MACUSA’s second great law enforcement challenge was the number of wizarding criminals who had fled to America from Europe and beyond, precisely because of the lack of organised law enforcement such as existed in their own countries.
The Magical Congress of the United States of America was established in 1693 with the introduction of the International Statute of Secrecy, as a direct result of the Salem Witch Trials, thus pre-dating the No-Maj formation of the United States of America by around a century.
In 1760, MACUSA relocated to Williamsburg in Virginia where then President Thornton Harkaway lived.
Harkaway bred Crups, which possess a great aggression towards non-magical people.They discussed whether to support their community or their country and whether to fight for liberation from the British Muggles.They also debated whether it was really their fight.They sought the advice of the Ministry of Magic to find out whether they intended to intervene on their side and they replied with only a four word letter — "Sitting this one out".Mc Gilliguddy replied with an even shorter message stating — "Mind you do".Rappaport’s Law was still in operation in the 1920s and several offices in MACUSA had no counterpart in the Ministry of Magic.