Mountain Lions are badass, and unfortunately, they are notorious for finding themselves in urban and suburban areas where they can pose a danger. Sadly, I think they are responsible for a few fatal attacks each year, though of course human beings and domestic dogs tend to be the most dangerous animals any American state, including California.
When I went to the La Brea Tar Pits a few years ago, and visited the museum, I was surprised to learn of all kinds of animals that used to exist in what is now California and the Western USA. American Lions, larger than their extant African counterparts, Dire Wolves, Elephants (including pygmy mammoths on Catalina Island), Camels, all kinds of cool fauna. I highly recommend it. The tar pits themselves are free, the museum costs a few bucks, there's a nice little park, and it's in a nice area of Los Angeles.