It's obvious how US 61-63-64-70-79 climbed the western approach of the Harahan Bridge and ran along cantilevered lanes on each side of the bridge. It's not so obvious how the US routes ran east of the bridge. How did these US routes run from the eastern end of the bridge to the current alignments? (US 63 ended at the foot of the bridge, and US 61 turned south, but the other 3 highways continued east.)
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fcartweb.geography.ua.edu%2Flizardtech%2Fiserv%2Fgetimage%3Fcat%3DNorth%2520America%2520and%2520United%2520States%26amp%3Bitem%3DStates%2FTennessee%2FTennessee1938a.sid%26amp%3Bpage%3D%26amp%3Bcp%3D0.053%2C0.705%26amp%3Blev%3D2%26amp%3Bwid%3D600%26amp%3Bhei%3D500%26amp%3Bprops%3Dimg%28Name%2CDescription%29%26amp%3Bbg%3Dffffff%26amp%3B&hash=144dc5b74b54800b2d610d90e12d424a21c2a39f)
http://condrenrails.com/MRP/maps/Oil-Company-Maps.htm
Looks like there is no mention of US 79 on that map. The last digit on the US 7x shield looks like US 78, but I didn't think it crossed the river.
That's definitely US 79 on the Arkansas side, where it ended then: http://usends.com/70-79/079/079.html
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi167.photobucket.com%2Falbums%2Fu126%2Fbugo348%2FAR19450611i1_zps7nvjmewy.jpg&hash=c36457525fee65bf72619807eb67cad6644d9465)
If you look at the third photo from the bottom in the following link, you can see that the roads and railroads were aligned differently on the Memphis side when the Harahan was the primary highway crossing.
http://condrenrails.com/MRP/Memphis-Yards/Other-Memphis-Railroad-Yards.htm