Tragic trials and convictions of witches and wizards in North America by Puritans who believed that magic was the devil possessing the accused person. Many of the accused were actually magical, although some were merely unfortunate No-Majs. At least two Judges were known Scourers (Pm:History of Magic in North America).
The trials cause greatly decreased immigration of magical folk to America, and led to the formation of the Magical Congress of the United States of America (MACUSA), whose first act was to put on trial the Scourers who betrayed their fellow magic-users. The second act by first President Josiah Jackson was to hire Aurors to hunt down wizarding criminals who had fled Europe, and who were known to help the Scourers (Pm:MACUSA).
Contrary to popular belief that hundreds of people died in the Salem Witch Trials, only about twenty were ever actually executed before the trials were stopped and those who had been convicted were released.
From the Web
Pottermore: History of Magic in North America by J.K. Rowling
Pottermore: Magical Congress of the United States (MACUSA) by J.K. Rowling
Smithsonian Institution: A Brief History of the Salem Witch Trials