[2] The county was created on January 21, 1854, and is named after James Fannin, a veteran who fought in the Texas Revolution.

[3] The county is named for Georgia native James W. Fannin,[4] who fought and died during the Texas Revolution.

Although the county was majority pro-secession at the beginning of the Civil War, wartime conditions inspired a notable number of anti-Confederate "Tories" as early as 1862, many of whom re-located to pro-Union areas of Tennessee for the duration.

This contributed to the postwar establishment of a countywide Republican Party earlier and more sustained than almost any other county in Georgia.

The vast majority of Fannin County is located in the Ocoee River sub-basin of the Middle Tennessee-Hiwassee basin.

A very small northeastern portion of Fannin County is located in the Hiwassee River sub-basin of the same Middle Tennessee-Hiwassee basin.

[8] As of the 2020 United States census, there were 25,319 people, 10,408 households, and 7,083 families residing in the county.

As of the 2010 United States census, there were 23,682 people, 10,187 households, and 7,016 families living in the county.

Since the 1870s, it has been solidly Republican, displaying voting patterns similar to those of East Tennessee.

Only three Democrats have won an absolute majority in the county since the Civil War: Samuel J. Tilden in 1876, William Jennings Bryan in 1900, and Georgia native Jimmy Carter in 1976, when he carried every county in his home state.

Besides Carter, Woodrow Wilson was the only Democrat to win even a plurality of the county's vote in the 20th century.