Saltpeter is the main ingredient of gunpowder and was obtained by leaching the earth from local caves.

Manson Saltpeter Cave in Big Indian Creek Valley was a smaller operation with four leaching vats.

[7] In the runup to the American Civil War, when Tennessee Governor Harris asked the State Legislature for a vote of secession, the two representatives from Fentress County (Reese T. Hildreth and R. H. Bledsoe) voted for secession.

Nevertheless, in Tennessee's Ordinance of Secession referendum on June 8, 1861, Fentress County voted by a margin of 651 to 128 to remain in the Union.

[9] Alvin York (1887–1964), a hero at the Meuse-Argonne Offensive during World War I, was born and lived in Fentress County.

[11] Fentress County includes part of Dale Hollow Reservoir and is drained by forks of the Obey and Cumberland Rivers.

Like much of East Tennessee, Fentress County is powerfully Republican, and has generally been favorable to that party ever since the Civil War.

Since then, only two Democrats, Southerners Jimmy Carter in 1976 and Bill Clinton in 1992 and 1996 have carried Fentress County.