Today, the flag of Mexico flies in celebration of Cinco de Mayo. The holiday celebrates the victory of the Mexican Army at the Battle of Puebla in 1862.
The holiday of Cinco De Mayo is associated with Mexican American culture. This connection was established in 1863, when the holiday was first celebrated in California. Interestingly, according to a UCLA article, the holiday is virtually ignored in Mexico.

Also belatedly flying today is the flag of the City of Oakland, California.

The City of Oakland incorporated on May 4, 1852.