Bienville established New Orleans in 1718, and Mardi Gras (it isn't until 1781 that we can refer to it as "Carnival") solidified itself as a New-Orleans icon by the 1730s. Around 1740, the first of a long history of Mardi-Gras balls and societies appeared. In 1856, the first floats (the Krewe of Comus, named after a Milton character) rode alongside flambeauxes and horses, and they were referred to as "tableaux cars").
In 1872, the Krewe of Rex was established as the king of Carnival, and the colors purple, green, and gold were attached to Carnival as a whole to honor the colors of Grand Duke Alexis Romanoff of Russia. The rest is history!
Have an good Carnival. Stay safe y'all.