The Mussel Rock area on the border of Pacifica and Daly City is best-known as a popular hang gliding spot. The on-shore area is quite riddled with gravel roads, trails, drainage ditches and debris, making it less attractive for hiking than other nearby areas like Mori Point and Pedro Point. The area has had significant mudslides over the years, and the city of Daly City has done a lot of work to prevent homes from falling into the ocean. In the meantime, this area is best used as an access to the beach on the north end of the park, which at low tide allows hikers to walk for miles to Thornton State Beach, Ocean Beach, and all the way to Lands End if the tide is right.
The area near Mussel Rock is quite interesting, both historically and geologically. It is best known as the point at which the San Andreas Fault crosses onto land from the northwest. It is also the site of the second-largest active slide area in California (the first being Devil's Slide) which collapsed quite dramatically during the 1906 earthquake. The location was involved in a 19th century railroad project and a short-lived coastal highway project, and a tunnel through the bluff near Mussel Rock itself that is still visible was once used by bootleggers and smugglers during Prohibition to hide contraband liquor.
Mussel Rock is a large sea stack just off shore at the south end of the park below the parking area. There is a nice viewing area quite close to Mussel Rock where the crashing waves, birds, and seals can often be comfortably observed without a lot of company.
Note: Dogs are allowed on-leash in the park and on the beach, and it is a very good idea to observe this regulation. There have been dogs attacked and killed here in daylight by coyotes as recently as spring of 2015!