Sierra County is part of Northern California's gold country region with an estimated population of 3291 people living within 1176 square miles . The largest towns are Downieville ( established during 1849 gold rush ) , Alleghany , Goodyears Bar , Sierra City , Gold Run , Loyalton among others . In addition to ranching there are two ski resorts nearby ( Yuba Pass & Boreal ) that offer winter sports coupled with other outdoor activities like fishing & boating at local bodies such as Lakes Basin Recreation area or Stampede Reservoir .