I did a bit of research on Cinco de Mayo, and while it celebrates the defeat of the French at the Battle of Puebla in 1862, Latinos in the West saw it as a <a href="http://www.civilwartalk.com/threads/cinco-de-mayo-originally-tied-to-civil-war.71925/".portent of the Confederacy's defeat as France was also supporting the Confederacy.
…According to Spanish-language newspapers at the time, this first group of multinational Latinos on U.S. soil identified with the Union Army’s fight against the Confederacy and often wrote pieces about the evils of slavery. Hayes-Bautista said these Latino immigrants were concerned about the Union’s lack of progress and Napoleon III’s interests in helping the South.
“It wasn’t until the news came about the Battle of Puebla that they got the good news they wanted,” said Hayes-Bautista. “Since Napoleon III was linked to the Confederacy, they saw the victory as the first sign that their side could win.”
They didn’t, of course, at least not for a few years. French forces took over Mexico after the Battle of Puebla, and installed Habsburg Archduke Maximilian as Emperor of Mexico. He was captured by Mexican forces five years later and put to death.
But in the years that followed, Latinos in California and the U.S. Northwest celebrated Cinco de Mayo with parades of people dressed in Civil War uniforms and gave speeches about the significance of the Battle of Puebla in the larger struggle for abolition, said Hayes-Bautista.
The holiday evolved here in the States into a Civil Rights Day:
The date received another jolt during World War II during the U.S. government’s “Good Neighborhood Policy” aimed at building good relationships with Mexico and during the Chicano Movement, when Mexican American activists adopted the day to reinforce civil rights demands. Two police beatings of Cinco de Mayo revelers — one in Houston in 1978 and the other in Washington DC in 1991 — resulted in riots and sparked protests and calls for reforms from Latino advocates.
and, finally to the Beer-soaked whatever it is today.