Republicans were interested in Labour, for the spoils of the 5 new Transcontinental Railroad Routes planned in the direct aftermath of the 1848 Mexican/American War by USA Secretary of War Jefferson Davis, the 1838 creation US ARMY Corps of Topographical Engineers, gave Davis a crew to work with, which included the likes of later adversaries Union generals Meade, Fremont, George McClellan and his right hand man Frederick Lander to map a route in Washington State to hook up a physically possible northern terminus of Tacoma with 2 of the routes, San Diego and Twin Cities Minnesota. (McClellan was a RR president in Chicago as that cities population blossomed, err burst between his mapping routes to be built, and his newfound responsibility Lincoln's Proclamation 80 gave him as rejoined Union army General to train up 75k troops in 6 wks, then use them to go on the offensive)
Regardless, a lot of Labor, iron, (Think Pittsburgh Steel and Carnegie) financing, and timber was needed to make Railroad Magnets and their families wealthy in perpetuity. Allegedly Karl Marx wrote and corresponded with Abe Lincoln, for he wanted the Irish/German Union Members to build it for a minimal wage, and then populate the areas with property taxpayers, rather than have the South build any with Slave Labour, as was Jefferson Davis and pals goal to get already bustling East coast Southern RR Hub of Atlanta to get the Southern two routes completed first.
Didn't happen, as needed congressional budget funding approval. Which went to the route built 1st.
Landers also mapped out much of the route eventually built first in 1869 hooking San Francisco/Sacramento's Chinese Labor built Sierra Nevada route (Leland Stanford, Huntington and boys via Schuyler Colfax)
to connect in Utah with the Irish/German Union Labor built track...
(Union Pacific / Credit Mobilier Scandal boys)
...all while the Reconstruction of the South was keeping them too busy to mount any effort or alternative manufacturing
