Was Tennessee in the civile war?

Yes, it was one of the four Upper-South slave-states that joined the Confederacy after Fort Sumter.

After the dramatic but indecisive Battle Of Manassas/Bull Run in Virginia, it was in Western Tennessee that the Civil War started to take shape, and U.S. Grant first came to notice here after liberating two major rivers, the Tennessee and the Cumberland.

In the Eastern half of Tennessee there was still a lot of pro-Union sentiment, but the self-taught Confederate cavalry General, Bedford Forrest, managed to dominate the region with endless attacks on the Union supply-lines.