All Good.
Just Recall that Jeff Davis was Secretary of War for Franklin Pierce, created and was in charge of the Topographical Corps of Engineers. Of which later Railroad Co. President Democrat George McLellan was placed in charge of Surveying two of the five Transcontinental connecting routes in the State of Washington, One N/S from San Diego to Tacoma/Seattle, the other E/W from Minneapolis to Tacoma/Seattle. Regardless, the Officers that were part of the Aztec Club of 1847, were predominantly involved as opposition to each other for the spoils of that war, as were immersed in the U.S. Civil War. Jeff Davis wanted the 2 southern routes of the 5 he had ordered surveyed completed first, as that would keep Atlanta as the main Trade Hub, and build it with Slave Labor. The middle route was completed by 1869. The other 4 that were all planned by subordinates of Jeff Davis, took a bit more time, yet were all Completed in U.S. Grant's lifetime.
The Free Soilers that became the Republican Party in Ohio, (Team of Rivals staunch Abolitionists, such as Salmon P. Chase, as well as Ohio Republicans Sherman's brothers, and Grant's father) and Northern Democrat Slave Owner Stephen Douglas and Lincoln maybe wanted Chicago to be the RR Hub instead of ATL, and got it done.
https://www.marxists.org/archive/marx/iwma/documents/1864/lincoln-letter.htm
Maybe,
Marx didn't care so much about ending slavery, as he did providing labor for his constituents, and win/win at the same time work for his working men of Europe to Migrate for the work.
https://en.wikipedia.org/wiki/List_of_members_of_the_Aztec_Club_of_1847
121 members of this exclusive club, were Generals on both sides in the US Civil War
(the new "Sons of Cincinnati" of Revolutionary War)