Gracias de Dios is the center of the land of the Lenca, the largest indigenous group in Honduras. Their most revered leader was Chief Lempira who, in the 1500s, managed to hold off invading Spanish forces. Though Lempira was ultimately killed by the conquistadors, he is celebrated every July 20 with this parade.
See full blog post - http://trans-americas.com/blog/2012/05/lempira-day-parade/