This quiet valley was once the site of the Gold-Rush-era town of Sucker Flat and of the Blue Point and Blue Gravel Mines, two of the richest hydraulic mines in California. Along with a number of other claims, they worked the gold-bearing placers laid under these hills by the Pliocene Yuba River. Water for hydraulicking came more than 20 miles from Nevada City in the Excelsior Ditch and from Grass Valley in the Tarr Ditch. The slurry was carried out into the present-day Yuba River through long sluice tunnels carved at great expense through hard basaltic rock. By 1877, a reported $13 million in gold had been mined, but the vast amounts of rock and gravel washed into the river caused tremendous destruction downstream. In 1884, the Sawyer Decision, supported by valley farmers, stopped the thriving industry in its tracks.