Cinco de Mayo - May 5th
The Battle of Puebla took place on 5 May 1862, near Puebla City in the Mexican state of Puebla during the Second French intervention in Mexico. The battle ended in a victory for the Mexican Army over the French Army. The Mexican victory at Puebla against a much better equipped and larger French army provided a significant morale boost to the Mexicans and also helped slow the French advance towards Mexico City.
The Mexican victory is celebrated yearly through a festival on the same date as the battle. It is primarily celebrated in the Mexican state of Puebla.
In the United States, this holiday has evolved into the very popular Cinco de Mayo holiday, a celebration of Mexican heritage. Celebrations surrounding the observance in the United States take on a significance beyond that in Mexico. They include displaying of banners and events highlighting Mexican culture, music, and regional dancing. School districts also hold special events to educate students about its historical significance. In the U.S., commercial interests the day by celebrating Mexican products and services with an emphasis on beverages, food, and music.
According to José Alamillo, professor of ethnic studies at Washington State University in Pullman, a study found more than 150 official events celebrating the day in the U.S.
https://en.wikipedia.org/wiki/Cinco_de_Mayo