Our camping trip recently was to Malakoff Diggins State Park, 20 miles north of Nevada City. Here is a "mini Yosemite Valley," carved out by miners enthusiastically directing pressurized water at the hillsides to make the gold run off. Since this flooded farms down the valley and was ecologically reprehensible, an 1884 court case ended the diggins. By 1940, the boomtown had shut down and in 1966 became a state park.
Malakoff Diggins has a really sweet little ghost town with about six buildings you can tour. It puts Goldfield to shame!
I was pretty much in ecstasy the whole time. Plus the campground itself (3,000 acres!) is really lovely. We had tentsite no. 27, which is closest to the diggins overlook. We had a great evening walk down to Blair Lake where we saw turtles, fish that swam in tight, fast, perfect circles, weird bugs, and best of all, really BIG frogs.
Here's Alan panning for gold. Gold flakes are terribly small, it turns out, more like gold molecules. We were told that the launderers would shake out the miners' clothes to collect up the gold dust.