Mardi Gras is the most important day in the New Orleans calendar, 24 hours that epitomize the city’s splendid culture.

Mardi Gras teaches the city’s children that fantasy is more precious than fact; that regal privilege is nothing more than a rhinestone-studded crown and a papier-mâche throne; that a parade is a community; that the mask is as important as what’s beneath it. Mardi Gras colors and defines every aspect of life in New Orleans, from the white-tie-and-tails balls of the...