A just-released book from UCLA professor David Hayes-Bautista, El Cinco de Mayo: An American Tradition, argues that Cinco's prominence in America isn't the result of just beer-company marketing.
It was a deliberate move on the part of Latinos in California:
Hayes-Bautista researched the origins of the holiday and found that, at the time the Mexicans were battling France in 1862, Latinos in California were worried about the U.S. Civil War making slavery a coast-to-coast practice that would ensnare all people of color.
He says it was a serious fear in California's Mexican-immigrant communities.
The French, they feared, would also reintroduce slavery to Mexico: The two fronts, in the American South and in Mexico, shared the same cause, anti-slavery, he says.
And so, when the Mexicans beat the French at the Battle of Puebla on May 5, 1862, those "Mexican patriotic assemblies" in California "deliberately created a public memory of it," according to UCLA.
Other Southwestern states, where Cinco remains strong, did the same, but Hayes Bautista says California, with Latinos made comparatively wealthy by the gold rush, was key in making Cinco de Mayo "an American tradition."
"Now we know why it's celebrated," he says.