Jackson TN remained behind Federal lines for the duration of the war. There were brief Confederate excursions into the area --

Nathan B. Forrest 'Christmas Raid' during December 1862.
Jeffrey Forrest's raid on Jackson in the summer of 1863.
Nathan B. Forrest's West Tennessee raids, April and October 1864.

Since the rail lines east, north and west had been cut, the only direction Harper could have taken would be south.