From Historic The Dalles Days
Wasco County is named for the Wascopam tribe of Indians that lived on the south shore of the Columbia River, near The Dalles, Oregon. Dalles City (now known as The Dalles) was designated the county seat when Wasco County was created on January 11, 1854 and was the second largest county in the country at the time. Wasco County was created from portions of Clackamas, Marion, Linn, and Lane Counties and consisted of all of Oregon Territory between the Cascade Range and the Rocky Mountains and from latitude 42deg. (the California border) to latitude 46deg. (the Washington border). This was one of the largest counties ever formed in the United States, originally consisting of 130,000 square miles. Courthouses were built in 1859, 1884, and in 1914. All three buildings are standing today and the 1914 building is still in use as the county courthouse. The Sheriff's department still operates a mounted patrol.
Over the years, seventeen other counties in eastern Oregon were created from Wasco County, which now consists of 2,387 square miles. It is bordered by two rivers, the Columbia to the north and the Deschutes to the east, and by the Warm Springs Indian Reservation on the south and Mt. Hood National Forest on the west. Wasco Wasco County shares political boundaries with Sherman, Wheeler, Jefferson, Clackamas, and Hood River Counties.
When Wasco County was created, Jan. 11, 1854, it comprised all the area of the Oregon Territory between the Cascade Range and the Rocky Mountains, an empire in itself. By successive takings for other states and counties, the area of Wasco County has been reduced to 2408 square miles. Wasco is the modern name for a tribe of Indians. Early writers used the name in many forms. Woss in "Fur Hunters of the Far West, v.1, p. 186," speaks of the Wiss-co-pam tribe. Lee and Frost in "Ten Years in Oregon, p. 176," give Was-co-pam. For references to various spellings, see "Handbook of American Indians, v.2, p. 918." About the time of the immigrations white people shortened the name to Wasco. The Wasco Indians were a Chinook tribe, formerly living on the south side of the Columbia River, in the vicinity of The Dalles. The name Wasco is said to be derived from the Wasco word wacq-o, meaning a cup or small bowl made of horn. "The Handbook of American Indians, v.2, p. 917", says this referred to a cup-shaped rock near the main village of the tribe, but Dr. William C. McKay, in an article in The Dalles Mountaineer, May 28, 1869, said that the name Wasco meant makers of basins, and that the literal meaning of the word was horn basin. Some of these basins were fantastically carved. Both of the explanations may be correct. Dr. McKay said that the locality of the city of The Dalles was called Winquatt, signifying a place surrounded by bold cliffs.
-- Source: Oregon Geographic Names, Sixth Edition, 1992, Lewis L. McArthur, Oregon Historical Society Press, ISBN O-87595-237-2.
The Dalles History