The nearest National Park to San Diego might be the new Joshua Tree National Park, about 150 miles away, but the San Diego Union-Tribune found plenty of links to the system in the county.
The sites range from the Cabrillo National Monument on Point Loma (generally No. 15 on the list of busiest in the nation), to the site of an ancient Kumeyaay village in the Cuyamaca Rancho State Park.
There’s very little about the prehistoric village in Cuyamaca and, honestly, I didn’t know about it until I read the story. There isn’t much on the web, but if you’d like to visit the park, consider taking my Curves, Dirt and Cuyamaca book for Kindle along as your guide.