Initially named Cave Valley, due to the limestone formations nearby, the town popped up around 1849 during the California Gold Rush. The population eventually grew to 4100 people.
It's unclear when the town went from Cave Valley to being Cool. One legend suggests that a beatnik named Todd Hausman bequeathed the name after passing through in the 1950s, but the veracity of that story is doubtful since the Cool Post Office was founded as early as 1885. According to Condé Nast Traveler, records show that a reverend named Peter Y. Cool came out to pan gold and settled in the town in 1850, possibly serving as the source of the change.
Whatever the origin of its name, the town of Cool has ample branding opportunities. There’s the Cool Grocery Store and the Cool Beerwerks brewery and restaurant, which specializes in Hawaiian-Japanese fusion cuisine. Cool has held the Way Too Cool 50K Endurance Run every year since 1990.
[h/t Condé Nast Traveler]