The Dalles is the county seat and largest city of Wasco County, Oregon, United States. The population was 13,620 at the 2010 census, and is the largest city on the Oregon side along the Columbia River outside the Portland Metropolitan area.
The site of what is now the city of The Dalles was a major Native American trading center for at least 10,000 years. The general area is one of the continent's most significant archaeological regions. Lewis and Clark camped near Mill Creek on October 25–27, 1805, and recorded the Indian name for the creek as Quenett.
The name of the city comes from the French word dalle, meaning either "sluice", akin to English "dale" and German T[h]al, "valley", or "flagstone", referring to the columnar basalt rocks carved by the river (in voyageur French used to refer to rapids), which was used by the French-Canadian employees of the North West Company to refer to the rapids of the Columbia River between the present-day city and Celilo Falls. Also in the same area was the Petite Dalles or Little Dalles, or Short Narrows. In French, "Les dalles" means "The slabs". When a river flows over hard flat rocks, it becomes shallow, and rapids are created.
The first use of the name Dalles, according to Oregon Geographic Names, appears in fur trader Gabriel Franchère's Narrative, on April 12, 1814, referring to the long series of major rapids in the river.