Grand Divisions of Tennessee
The border between East Tennessee and Middle Tennessee is on the Cumberland Plateau. It was a major barrier to travel during much of the state's early history. It is close to the line between the Eastern and Central time zones. All but three counties of East Tennessee (Bledsoe, Cumberland, and Marion) are in the Eastern Time Zone. Middle and West Tennessee are entirely in the Central Time Zone. The reach of the Tennessee River that flows northward to Kentucky from Mississippi and Alabama marks the border between Middle and West Tennessee starting from the northern border of Hardin County. It is split down the middle by the Tennessee River but is located wholly in West Tennessee.