4,000-4,300 horsepower diesel locomotive built from 1993 to 2004.

Over 1,100 were built, with only 15 built specially for Conrail and over 350 built for the Burlington Northern (with orders continued into the BNSF merger with another 800 or so units ordered later on). Later customers such as CSX,and the Alaska Railroad (ARR) as well as TFM (subsidiary of KCS; Kansas City Southern) eventually purchased units up until the introduction of the SD70ACe.

The SD70ACe serves as the SD70MAC's successor; having more advanced microprocessor controls and being EPA Tier 2 compliant.

Many are still currently in service, with the exception of several stored, wrecked, and a few retired units.

During the early-1990's, EMD teamed-up with German engineering company, Siemens, to experiment with having an average, modern, North American type of freight diesel locomotive to become capable of providing AC-traction drive currents, and thus providing a high-horsepower rating and lower fuel consumption for railroads which had an ever-increasing demand for saving fuel consumption by using a lesser amount of units to haul most of their trains. The solution to all these problems was resolved with the experimental SD60MAC, which proved to be an initial success after several demonstrations with the Burlington Northern's Powder River coal trains through Wyoming and Montana. Because of the success of the SD60MAC, the development for the SD70MAC first A.C. production locomotive built by EMD. Although the SD60MAC was successful, the BN; however, disliked the cab design due to being uncomfortable with rail employees who tested the units. Such complaints consisted of: heavy vibrations, noise pollution from the prime mover, and an unusual amount of cab visibility due to the cab design originating from an earlier SD60M, yet with a slightly different window placement which deemed to be too "foreign"; meaning that the design looked more Canadian, and such design was originally disliked by employees who drove some of BN's earlier SD60M units ordered and received several years earlier.

The EMD SD70MAC was first introduced in early 1993, and began production later-on during the same year after numerous tests and improvements were made. The first order was 350 units were received from the BN in mid-1993 to late-1995. BN eventually began to slowly replace their fleets of aging SD40-2 units (aside from their GE U30C and Dash 7 units) assigned to their Powder River Coal Trains in favor of their new, modern, high-tech AC-traction SD70MAC units; which were proven to replace 5 SD40-2's on an average coal train, with only 3 to 4 being necessary (two front, two rear) with the SD70MAC units having a DPU (Distributed Power Unit) capability, which was originally introduced with the SD60MAC.

Towards the end of the SD70MAC's introduction, a new rival from GE appeared: the AC4400CW, which completely dominated over the SD70MAC in production sales. Although more successful in popularity, the AC4400CW had more short-lived warranties with most railroad's fleets which had to be renewed unlike the SD70MAC; hence the reason why the Burlington Northern decided to deny every opportunity from GE due to already having numerous warranties from leasing companies which required numerous payments.

Today, the SD70MAC can still commonly be seen hauling various coal trains or being assigned to coal drag service on the BNSF, as well as being a common hauler on the TFM portion of the KCS (Kansas City Southern). Former Conrail SD70MAC units can still be seen on the CSX system, yet no longer bear or wear their once-exclusive livery which was very similar to their SD80MAC livery, while the Alaska Railroad's fleets of SD70MAC units can be seen in general revenue service on both of their freight and passenger trains (being the only US Class 2 railroad to actually have both revenue freight and passenger service).