Most Americans are unaware of its original ties the U.S. Civil War, links to abolition and promotion of civil rights for blacks.
Cinco de Mayo commemorates the 1862 Battle of Puebla between the victorious ragtag army of largely Mexican Indian soldiers against the invading French forces of Napoleon III.
David Hayes-Bautista, author of "El Cinco de Mayo: An American Tradition," said during the Gold Rush when thousands of Latinos came to California, the immigrants linked the battle to the Civil War since Napoleon III supported the Confederacy.
The first Cinco de Mayo celebrations had U.S. Civil War themes but changed over time. Today the holiday is heavily promoted by restaurants and beer companies.