Backbone Road Bridge

There was a mill, named Duley's Mill, established circa 1820s, on the Boone County side of Cedar Creek near the base of the Devil's Backbone, that high, steep ridge, down which the steep Backbone Road you refer to led to the Cedar Creek. Cedar Creek was used to power the mill. Evidently, the mill was quite the social center of the day. The "why" of the bridge was to give access to the mill from Calloway County on the other side of Cedar Creek. I believe that there was originally a ford across the creek that was probably replaced with a wooden bridge and later the metal truss bridge. The "when" it was built and later abandoned I do not know, except that it likley correlated with the closing of the mill, probably in the early 1900's. I am looking into this; the mill was owned by the Duleys at least until 1895 and later owned by W. H. Renoe, a Dentist who also had his practice at the mill. After the mill closed, travelers desiring to cross the creek could go upstream a short distance and use the Rutherford Bridge, hence being able to avoid the steep road going up the Devil's BackBone. The Rutherford Bridge was a similar metal truss bridge, also later abandoned, that was converted to a foot bridge circa 1983 by the Boy Scouts, giving access to hiking what was originally known (and still is, popularly) as the Devil's BackBone trail and is now known as the Cedar Creek Trail.

Does anyone know why this bridge was abandonded? or why it was originally built? The road leading down to it is nearly impossible to drive even in a pickup.