Cinco de Mayo or 5th of May is the celebration of the Mexican victory over the French Army in 1862. The battle took place in Puebla, Mexico and this is in fact the only part of Mexico that still celebrates Cinco de Mayo today with vigor.
In short, a rag-tag group of Mexican soldiers exhausted, outnumbered and poorly supplied were able to fend off the French army from capturing Puebla de Los Angeles. This was an amazing victory for the local Mexican army as well as a major point of pride for the residents of Puebla.
The U.S. has since adapted the holiday as practically its own. According to Valerie Menard (The Latino Holiday Book), popularity of the holiday in the U.S. started back when in California when it was part of Northern Mexico. The Mexican population began celebrating the holiday to show solidarity with their "mother country". Later, in 1864 a San Francisco resident hosted a Cinco de Mayo dance that became an annual event through the 1950's. Today, many cities host Cinco de Mayo parades and festivities.
So grab your molcajete, stock up on fajita fixin's and join in on the fun. If you would like to read more about the history this is a good source: Read More from History.com
Traditional festival drinks include simple aguas frescas like agua de tamarindo or agua de jamaica. For the adults try a traditional margarita or famous West Coast La Tuna (prickly pear) drink.