We have seen the pattern that most big towns in the Midwest in 1850 were on either a big river or a canal. And the businessmen of those towns understood that they needed to get on a railroad route to avoid becoming obsolete. So I assume it was the leaders of Clarksville, TN that charted the Memphis, Clarksville & Louisville Railroad in the states of Tennessee and Kentucky on Jan. 28, 1852. But to achieve the goal of their charter, they needed to build just 86 miles of track from Paris, TN to Guthrie, KY to connect the Memphis & Ohio Railroad with the Memphis branch of the Louisville & Nashville to create a route between Memphis and Louisville that would run through Clarksville. [RailFanning (don't access because of a poor taste of advertising)]
The first trains started running in 1961 when the bridge across the Tennessee River was completed in Danvillle, TN. Unfortunately, they did not collect much revenue before the Union Troops of the Civil War stopped traffic on the railroad. Traffic resumed in 1866.
My 1928 RR Atlas indicates the whole route from Memphis to their mainline in Kentucky was then owned by the L&N. It also reminded me that the Kentucky Dam had yet to be built because two forks of the Kentucky Lake would have flooded the indicated route. The reservoir of that dam finished filling in 1945. I checked my 1973 RR Atlas for the new alignment, but it appeared to be the same. There are two reasons why the alignment did not change. One is that the atlas did not draw the route correctly It shows it leaving Paris to the northeast, and then going east. Abandoned Rails shows the route left Paris to the southeast and then worked its way north and east to Clarksville. The second reason is that the L&N raised the new bridge that they had just built in 1931-32 when they learned in 1937 that the area was going to be flooded.
As indicated in Abandoned Rails, the segment from Paris, TN to beyond Cumberland City was abandoned in 1985. But studying a satellite image shows that there are still tracks between Cumberland City and Clarksville.. And R.J. Corman's Memphis Line (RJCM) shows it operates between Cumberland City and Memphis Junction with a branch to Lewisburg, KY. Memphis Junction is on the original L&N mainline, which is now owned by CSX.