The Dalles had served initially as a way station on the emigrant road to the Willamette Valley. The construction of a pioneer road over the Cascades in 1845, and the Donation Land Act of 1850 encouraged families to settle in the area. Over the following years, Wasco County was a major transportation hub for both river traffic and inland traffic. The river traffic on the Columbia River was profoundly affected in 1935 by the building of Bonneville Dam in Multnomah County and by The Dalles Dam in 1957 in Wasco County. The county's economy is based upon agriculture (orchards, wheat farming, livestock ranching), lumber, manufacturing, electric power, transportation, and tourism. Aluminum production was previously a major support of the local economy, but electrical price fluctuations and a slump in global aluminum prices has forced the closing of a number of local aluminum foundries.
According to the U.S. Census Bureau, the county has a total area of 6,204 km² (2,395 mi²). 6,167 km² (2,381 mi²) of it is land and 37 km² (14 mi²) of it is water. The total area is 0.60% water.
As of the census of 2000, there are 23,791 people, 9,401 households, and 6,505 families residing in the county. The population density is 4/km² (10/mi²). There are 10,651 housing units at an average density of 2/km² (4/mi²). The racial makeup of the county is 86.58% White, 0.30% African American, 3.81% Native American, 0.80% Asian, 0.50% Pacific Islander, 5.65% from other races, and 2.36% from two or more races. 9.31% of the population are Hispanic or Latino of any race.
There are 9,401 households out of which 30.20% have children under the age of 18 living with them, 54.80% are married couples living together, 9.90% have a female householder with no husband present, and 30.80% are non-families. 26.10% of all households are made up of individuals and 11.50% have someone living alone who is 65 years of age or older. The average household size is 2.47 and the average family size is 2.96.
In the county, the population is spread out with 25.40% under the age of 18, 7.40% from 18 to 24, 25.20% from 25 to 44, 25.40% from 45 to 64, and 16.70% who are 65 years of age or older. The median age is 40 years. For every 100 females there are 97.90 males. For every 100 females age 18 and over, there are 95.10 males.
The median income for a household in the county is $35,959, and the median income for a family is $42,412. Males have a median income of $36,051 versus $21,575 for females. The per capita income for the county is $17,195. 12.90% of the population and 10.30% of families are below the poverty line. Out of the total people living in poverty, 17.70% are under the age of 18 and 7.30% are 65 or older.
Celilo Falls on the Columbia River served as a gathering place and major trading center for the local Native Americans, including the Wasco, Paiute, and Warm Springs tribes, for thousands of years. These rapids came to be named Le Grand Dalles de la Columbia or "The Great Falls of the Columbia" by the French Canadian fur traders.
The Territorial Legislature created Wasco County on January 11, 1854 from the parts of Clackamas, Lane, Linn and Marion counties, that were east of the Cascade Range -- which included most of Idaho, and parts of Montana and Wyoming. At the time of its creation, it was the largest county in the United States, consisting of 130,000 square miles. As Washington Territory and other Oregon counties were split away, Wasco county was reduced to its far humbler size.
The Dalles was designated the county seat with the creation of the county, and has been its only location.
Wasco county attracted international attention in the 1980s, when Bhagwan Shree Rajneesh came to the United States and settled for several years at a marginal ranch called "The Big Muddy", but later known as Rajneeshpuram. Disagreements over zoning rules and building codes in the beginning continued to escalate between not only his followers and the inhabitants of Wasco County, but eventually with the rest of the state. His followers, known as Rajneeshes, settled en bloc in Antelope, Oregon and were able to elect a majority of the town councillors. Acerbic and impolic, if not hostile comments by his public spokeswoman, Ma Annand Sheela, only increased tensions, and were not helped by Rajneesh's vow of silence. When the Rajneeshes subsequently recruited homeless people from across the United States to settle at Rajneeshpuram, it was widely seen as an attempt to use the ballot box to seize control of Wasco county. But perhaps the most bizarre turn of events was when an outbreak of salmonella in a salad bar at a restaurant in The Dalles was traced to the acts of his followers. About this time, Sheela was removed from her post in the Rajneesh's service, and shortly afterwards left for Germany.
This chapter finally ended in 1985, when Rajneesh was arrested in North Carolina as he was fleeing the U.S. On October 23, 1985, a federal grand jury in Portland had secretly indicted Rajneesh, Sheela, and six of his other followers for immigration crimes. Two days later, a Wasco County grand jury returned indictments against Sheela and two others, charging them with the attempted murder of Swami Devaraj, the Bhagwan's personal doctor. He entered an "Alford plea," also called a no-contest plea, and given a suspended sentence on condition that he leave the country.
As of 2000, the former Rajneesh ranch is now known as "Wildhorse Canyon". It is owned and operated by Young Life Ministries, a Christian organzation providing camp services for youth.