​At the turn of the 20th century, the people of the Hood River region in the northwest portion of Wasco County expressed a desire for political separation from the parent county. The passage of a statewide initiative established Hood River as the 34th county of the state. It was made official by a governor's proclamation on June 23, 1908. Hood River County was named after the Hood River and Mt. Hood which are both located in its boundaries. Mt. Hood was named in 1792 after Lord Hood (Samuel) who served in the British Navy during the American Revolutionary War.

The county's boundaries have since remained unchanged. It is bordered by Wasco County to the east, by Clackamas and Multnomah Counties to the west, and by the Columbia River to the north. Hood River County is the 2nd smallest county by size in the state, outranking only Multnomah County, with a total area of 533 square miles.

The City of Hood River, first platted in 1881, is the county seat. The first county courthouse was an old primary school building. In 1937, after failing to approve a new courthouse, the county was forced to purchase the Butler Bank Building, which housed the county government until 1954 when the present courthouse was constructed. Most county administrative offices are now housed in the county's nearby Business Administration Building.

Initially, county officials included the county judge, two county commissioners, sheriff, clerk, treasurer, assessor, school superintendent, surveyor and coroner. In 1964, Hood River County adopted the home rule form of government. A five-member elected board of commissioners creates ordinances and resolutions to govern the county. The commission appoints a county administrator to oversee operations of county services. Except for an elected sheriff, all county department heads are selected by and responsible to the commission. Several specialized advisory boards, committees, and commissions give the board advice and recommendations concerning various county services.

The population of Hood River County in 2013 was 23,295. This was a 4.2% increase from 2010.

The first permanent settlers in Hood River County filed a donation land claim in 1854; by 1880 17 families lived in the region. By the late 19th century farmers of Japanese, Finnish, German and French ethnicity settled in the valley. The Columbia River Highway was completed in 1922 from Portland to The Dalles, making the towns of Hood River County more accessible to people and commerce from throughout the Columbia River Gorge and the state.

The principal industries of Hood River include agriculture, recreation, timber and hydroelectric production. The fertile Hood River Valley has an ideal climate for to produce apples, cherries, peaches and pears. It also offers recreational activities such as snow skiing, yachting and fishing which bring people and capital to compensate for the decline in logging and hydroelectric production. The Columbia River near Hood River is a premier windsurfing area and attracts windsurfers and kiteboarders from around the world.