- A UCLA professor of medicine happens upon the true origins of Cinco de Mayo, he says in a book
- It's an American holiday -- not a Mexican one -- with roots in the Civil War
- Latinos in the American West cheered Mexican army's defeat of French in 1862
- The French sympathized with Confederacy, and U.S. Latinos supported the Union
Los Angeles (CNN)Cinco de Mayo -- the unofficial U.S. holiday long believed to have been imported, with celebratory beer, from Mexico -- isn't a Mexican holiday at all but rather an American one created by Latinos in the West during the Civil War, according to new research by a California professor.