San Joaquin County was named for the San Joaquin River which dates to 1805–1808, when Spanish explorer Gabriel Moraga was surveying east from Mission San José in order to find possible sites for a mission. Moraga named a tributary of the river for Saint Joachim, husband of Saint Anne and father of Mary, the mother of Jesus.Of course, there was also the legendary bandit and notorious outlaw in the Central Valley named Joaquin Murrieta. Legends about him arose during the California Gold Rush of the 1850s, but evidence for a historical Murrieta is scarce. Contemporary documents record testimony in 1852 concerning a minor horse thief of that name. Newspapers reported bandido named Joaquin, who robbed and killed several people during the same time. A California Ranger named Harry Love was assigned to track down Murrieta and was said to have brought his head in for the bounty.
These days, it would be more appropriate to have Joaquin County named after the infamous outlaw rather than the father of Mary. But the good sheriff is turning that around.