Sierra, a N. E. county of California, bounded E. by Nevada, and drained by the North and Middle forks of the Yuba river; area, 830 sq. m.; pop. in 1870, 5,619, of whom 810 were Chinese. It is situated among the Sierra Nevada mountains, and but little of it is less than 3,000 ft. above the sea. There are several isolated peaks, the most conspicuous of which are Table mountain, more than 6,500 ft. high; Saddle mountain, a little lower; and the Sierra buttes, 8,300 ft. high. Nearly the whole county is underlaid by auriferous slates, generally covered by volcanic accumulations. It is one of the chief gold-producing counties in the state. The surface is covered with a heavy growth of coniferous trees. The land suited to agriculture or grazing is mostly confined to a few small valleys and mountain flats. The climate in winter is rigorous. The chief productions in 1870 were 7,794 bushels of wheat, 8,250 of oats, 10,415 of barley, 8,451 of potatoes, 39,200 lbs. of butter, and 7,466 tons of hay. There were 464 horses, 887 milch cows, 2,257 other cattle, 402 sheep, and 437 swine; 13 saw mills, 1 machine shop, and 6 quartz mills.