Carnival is meant to mark time between the Christian observances of Twelfth Night and Ash Wednesday (the start of Lent). The day preceding Ash Wednesday is Mardi Gras, and the festivities are seen by some as the last "hurrah" of excess before observing atonement and moderation in the lead-up to Easter.
The first more official celebration took place in 1856. Some historians believe that the first American Mardi Gras took place as early as 1699.
The State of Louisiana declared Mardi Gras to be an official holiday in 1875.
Mardi Gras will be celebrated tomorrow from parts of the United States, to the Caribbean, South America, and parts of Europe. The Mardi Gras colors were assigned in 1892, with purple symbolizing justice, green for faith, and gold for power.