There are 9 US Post Offices in Amador County serving a total of 37,676 residents equating to 4,186 residents per post office. It's estimated that approximately 60,135 packages are handled across the 9 county post offices annually. Amador County, officially the County of Amador, is a county located in the U.S. state of California, in the Sierra Nevada. As of the 2010 census, the population was 38,091. The county seat is Jackson. Amador County bills itself as \"The Heart of the Mother Lode\" and lies within the Gold Country. There is a substantial viticultural industry in the county.