Union Pacific’s #1979 is the railines's 18th commemorative locomotive honoring the company’s nine Employee Resource Groups (ERGs) and the work they do supporting diversity, inclusion and equality. The unit commemorates the year Union Pacific’s first ERG was established in 1979.

Introduced in 1992, EMD SD70M was a 4000 horsepower locomotive that ran on EMD’s new steerable truck design, known as the HTCR-II radial truck. This new truck allowed the locomotive to transfer its power to the rails more efficiently, which in turn enabled two SD70M locomotives to pull a train that would have taken 3 SD40-2’s to pull. The DC brother of the SD70MAC, the SD70M was primarily put to work hauling coal trains due to its high pulling capacity.