[3] The county was established by the Tennessee General Assembly on November 7, 1821,[4] and was named for Governor William Carroll.

In general, the alignment of voters with the two major parties has shifted since the late 20th century, but Carroll County had a different history.

Conservative whites in the upland and Deep South largely shifted away from the Democratic Party in the late 20th century to the Republican Party, but Carroll County had only briefly supported Democratic presidential candidates in the 20th century: 1912, when Southerner Woodrow Wilson was elected; from 1932 to 1948, for Franklin D. Roosevelt and Harry Truman during the Depression and years of World War II and after, and Southerners Lyndon B. Johnson in 1964, Jimmy Carter in 1976, and Bill Clinton in 1992–1996.

[16] But at the time of the American Civil War and for decades after, Carroll was the northernmost county in the Unionist Republican bloc, made up of Wayne, Henderson, Hardin and McNairy counties, within historically Democratic West Tennessee.

In Tennessee's Ordinance of Secession referendum on June 8, 1861, Carroll County voted to remain in the Union by a margin of 1,349 to 967,[17] whilst earlier on February 9, 1861, county voters voted against holding a secession convention by a margin of 1,495 to 678.

[18] Historians note that the enclave developed this way because, unlike in the fertile Delta, this region of the Highland Rim had soils that were shallow, humus-poor and easily erodible.

Settlers who were poor could acquire land here, as the area could not support the plantations more typical of Middle and West Tennessee, which were dependent on the labor of enslaved African Americans.