The work on Alexander's Bridge and nearby Slough Bridge includes rebuilding stone masonry walls and replacing wood guardrail.
During the Civil War, Union soldiers took up planks on the bridge then at the site to prevent Confederates from crossing.
The Federal Highway Administration in May awarded a $1.6 million contract to Bluegrass Construction Corp. of Lexington, Ky.
The battlefield park's resource management chief told the Chattanooga Times Free Press that the contractor has done similar work before.
"The stonework guys are there, and I guess it's going to be like working a jigsaw puzzle — taking it apart and putting it back together. But they've done this kind of stuff before," said Jim Szyjkowski, chief of resource management at the battlefield park.
The current Alexander's Bridge dates back to 1907.
The work will reopen Alexander's Bridge Road. Alexander's Bridge was closed to all but pedestrian and bicycle travel in early 2009 after it failed an inspection. Slough Bridge was closed to vehicles after it was damaged by flooding in late 2009.
A steel span section of Alexander's Bridge will be recycled in Walker County for eventual use in a regional greenway system.
Park officials said the bridge work is scheduled to be complete, and Alexander's Bridge Road should be reopened, before January.