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.
The first groups from the eastern U.S. following the Oregon Trail passed through the area on their way to the Willamette Valley, unaware of the potential wealth they passed over. At Flagstaff Hill, near Baker City, of wagon ruts left by immigrants can still be seen.
In 1861 gold was discovered and Baker County became one of the Northwest's largest gold producers.
On September 22 of the following year, the state assembly created Baker County from the eastern part of Wasco County. Later, Union County and Malheur County were created from this county. The boundaries were adjusted for the last time in 1901, when the area between the Powder River and the Wallowa Mountains was returned to Baker County.
The original county seat was at Auburn. While at first a booming mining town with 5,000 inhabitants, once the gold was mined out Auburn's population dwindled, and county citizens eventually voted in 1868 to make Baker City, incorporated in 1874, the new county seat.
The population of Baker County nearly quadrupled between the years 1880 and 1910. This growth was largely a product of the emergence and expansion of the Sumpter Valley Railroad and several of its spur lines, which helped lumber and mining operations to develop and grow.
In 1914 Fern Hobbs, on behalf of her employer Governor Oswald West, declared martial law in the Baker County city of Copperfield. This was the first declaration of martial law in the state since the American Civil War.