Nola links to the Wikipedia article on king cakes which is pretty thorough on king cake history. I’ve found a couple of others, and would recommend Mardi Gras Unmasked’s web page on the subject. It goes a bit deeper into the local traditions, including a good overview of the Twelfth Night Revelers’ ball. A large, stylized mock king cake made of separate compartments is “sliced” by overly large knives made of wood. The ladies of the court are called out and given a “slice” which usually contains a silver bean, the maid given the slice with the golden bean becomes queen.
There’s more to Mardi Gras tradition than parades, beads, doubloons and king cakes. The costumed balls thrown by various krewes and organizations like the Twelfth Night Revelers are heralded by elaborately designed and printed invitations. The invitations evolved into works of art themselves and have become treasured keepsakes among the families who are lucky enough to receive them. Souvenir favors handed out at the balls also become collectible treasures.
Mardi Gras: It’s Carnival Time in Louisiana is the Louisiana State Museum’s permanent exhibit at the Presbytyre next to St. Louis Cathedral. Examples of the giant knives, stylized king cake pieces from Twelfth Night Revelers are on display there. Many examples of invitations, ball favors, costumes, gowns and the kings, and queens’ jewels from krewes over the years are on display.
Along with the page at Mardi Gras Unmasked, I also ran across an article in a Northshore publication with a history of Mardi Gras ball invitations and favors and resources available for studying them at The Historic New Orleans Collection and the Louisiana State Museum. It also has an article with good info on king cakes, their history, and a run-down of Northshore king cake bakers. One of the Northshore bakeries in the article is run by a couple of French ladies who bake a traditional Galette des Rois, a puff pastry concoction filled with almond paste.