The area that would one day become Guatemala, El Salvador, Nicaragua, Costa Rica, and Honduras declared their independence from Spain on September 15, 1821. It took a few years of searching around first joining the Mexican Empire then trying to form their own Central United States till they became separate countries.
Today the celebration last many weeks and the preparations last even longer. There are marching bands and parades. Speeches are given and the military will pass in review for the presidents of the countries. Many people will dress in traditional clothing and show their pride in their country and independence.
One aspect I find really interesting is the torch that is run the length of the countries signifying the freedom being announced to all the states. The run ends in Costa Rica which was the last area to hear about the independence being so far removed.
So Happy Independence Day Guatemala, El Salvador, Nicaragua, Costa Rica, and Honduras!
Some additional links:
http://2backpackers.com/1804/photo-of-the-day/guatemala-independence-day
http://www.travelblog.org/Central-America-Caribbean/Costa-Rica/Heredia/blog-92337.html
http://costa-rica-guide.com/travel/index.php?Itemid=676&id=443&option=com_content&task=view