Gilliam County is a county located in the U.S. state of Oregon. As of the 2010 census, the population was 1,871, making it the third-least populous county in Oregon. The county seat is Condon. The county was established in 1885 and is named for Cornelius Gilliam, who commanded the forces of the provisional government of Oregon after the Whitman Massacre.
The Oregon Legislative Assembly created Gilliam County on February 25, 1885, from the eastern third of Wasco County after residents complained that they were too far from their county seat in The Dalles. The first Gilliam county seat was at Alkali, now Arlington. The question of a permanent county seat was placed on general election ballots in 1886, 1888, and again in 1890, when voters chose to move the county seat to Condon, known to early settlers as "Summit Springs." Once the question of the location of the county seat was settled, voters in Gilliam County proved reluctant to provide a courthouse in Condon. The county government operated out of a two-room house until 1903, when the county court appropriated money to construct a courthouse. This courthouse burned down in 1954 and was replaced the following year with the current courthouse.
Thereafter, apparently nothing much happened until the Shepherds Flat Wind Farm, an 845 megawatt (MW) wind farm, began construction in Eastern Oregon, in both Gilliam and Morrow counties, near Arlington. Approved in 2008 by state regulators, groundbreaking came in 2009. The wind farm was being built by Caithness Energy using General Electric (GE) 2.5 MW wind turbines, and it will supply electricity to Southern California Edison. In April, 2011, Google announced they had invested $100 million in the project. The wind farm was estimated to have an economic impact of $16 million annually for Oregon.