So here is a little history(provided by KidzWorld):
In the year 1500, Spain conquered Mexico and named it New Spain. Life was hard under Spanish rule and many of the native Mexicans (Mayas and Aztecs) were forced into slavery. More than 300 years later, on September 16, 1810, a priest named Father Miguel Hidalgo y Costilla started a revolt against the Spanish. The Spanish were finally defeated in 1821 and Mexico had their freedom again!
Some quick facts:
Today streets, houses, buildings and cars are decorated everywhere in the world in the Mexican National Colors Green, White, & Red. Food is very important during this celebration with some most noted ones including ponche(made of fruits of the season-: guayabas, sugarcane, raisins and apples),Mole Poblano, Chiles en Nogada, Guacamole and chips. Live Mariachi Music bands play to the delight of all present.
Finally – The celebration reaches the high point when the crowd joins in proudly shouting out the names of the heroes of our Independence, to end with the exciting VIVA MÉXICO!