According to the History.com website:

“Though early French settlers brought the tradition of Mardi Gras to Louisiana at the end of the 17th century, Spanish governors of the province later banned the celebrations. After Louisiana became part of the United States in 1803, New Orleanians managed to convince the city council to lift the ban on wearing masks and partying in the streets. The city's new Mardi Gras tradition began in 1827 when the group of students, inspired by their experiences studying in Paris, donned masks and jester costumes and staged their own Fat Tuesday festivities.”