There are 18 US Post Offices in Calaveras County serving a total of 45,486 residents equating to 2,527 residents per post office. It's estimated that approximately 72,601 packages are handled across the 18 county post offices annually. Calaveras County, officially the County of Calaveras, is a county located in the U.S. state of California. As of the 2010 census, the population was 45,578. The county seat is San Andreas, and Angels Camp is the only incorporated city. Calaveras is the Spanish word for skulls; the county was reportedly named for the remains of Native Americans discovered by the Spanish explorer Captain Gabriel Moraga. Calaveras County is located in both the Gold Country and High Sierra regions of California. Calaveras Big Trees State Park, a preserve of Giant Sequoia trees, is located in the county several miles east of the town of Arnold on State Highway 4. Credit for the discovery of giant sequoias here is given to Augustus T. Dowd, a trapper who made the discovery in 1852 while tracking a bear. When the bark from the \"Discovery Tree\" was removed and taken on a tour around the world, the trees soon became a worldwide sensation and one of the county's first tourist attractions. The uncommon gold telluride mineral calaverite was discovered in the county in 1861 and is named for it. Mark Twain set his story, \"The Celebrated Jumping Frog of Calaveras County\", in the county. The county hosts an annual fair and Jumping Frog Jubilee, featuring a frog-jumping contest, to celebrate the association with Twain's story. Each year's winner is commemorated with a brass plaque mounted in the sidewalk of downtown Historic Angels Camp and this feature is known as the Frog Hop of Fame. The California red-legged frog, feared extinct in the county by 1969, was rediscovered in 2003."