There are 10 US Post Offices in Baker County serving a total of 16,162 residents equating to 1,616 residents per post office. It's estimated that approximately 25,796 packages are handled across the 10 county post offices annually. Baker County is a county located in the U.S. state of Oregon. As of the 2010 census, the population was 16,134. The county seat and largest city is Baker City. The county was split from the eastern part of Wasco County. Union County and Malheur County were set off from Baker County in 1864 and 1887 respectively. It is named for Edward Dickinson Baker, a senator from Oregon who was killed at Ball's Bluff, a battle of the Civil War in Virginia in 1861. Baker County is included in the 8 county definition of Eastern Oregon."