[2] The county is named for James Knox Polk, the 11th president of the United States.

The Oregon Provisional Legislature created Polk County from Yamhill District on December 22, 1845, granting to it the entire southwestern portion of present-day Oregon to the California border.

The first county seat was a settlement on the north side of Rickreall Creek named Cynthian (also known as Cynthia Ann).

During the 1880s and 1890s, there were a series of unsuccessful efforts to move the county seat to nearby Independence.

[3] About two thirds of Polk County, the western part, is forest, mostly of the coniferous and mixed varieties, bordering on temperate rain forest around Laurel Mountain, the wettest place in Oregon.

23% of all households were made up of individuals, and 9.8% had someone living alone who was 65 years of age or older.

Though Polk County is located in western Oregon, politically it falls in line with the eastern side of the state.

[14] These numbers show a shift toward the Republican candidate when compared to the 2008 presidential election, in which 48.92% of Polk County voters voted for Republican John McCain, while 48.43 percent voted for Barack Obama, and 2.64 percent either voted for a Third Party candidate or wrote in a candidate.

[15] Obama's 2008 performance was the best by a Democrat since Lyndon Johnson carried the county in 1964; the only other Democrats to ever carry Polk County have been Franklin Roosevelt in 1932 and 1936, Woodrow Wilson in 1912, and William Jennings Bryan in 1896.

[16] The major industries of the county are agriculture, forest products, manufacturing, and education.

Polk County has the second-largest area devoted to viticulture in Oregon, at 1,322 acres (5.35 km2).