- Errol City is a fictional city created by J.K. Rowling, the author of the Harry Potter series. It is a wizarding city located in the United States and is home to Ilvermorny School of Witchcraft and Wizardry, the American equivalent of Hogwarts School of Witchcraft and Wizardry. Despite being a fictional city, Errol City is often referenced in fanfiction and other works inspired by the Harry Potter series.