The Ann Arbor Railroad (1895–1976) had declared bankruptcy and was included in the assets of Conrail, formed on April 1, 1976. The MIRC operated until October 7, 1988, when the Ann Arbor Acquisition Corporation acquired all assets.
The Michigan Interstate Railway operated equipment that had been used by the previous operator, the Ann Arbor Railroad. The Ann Arbor Railroad purchased ten new EMD GP35s in 1962 that were built and delivered in 1963. When the MIRC assumed operations in 1977, the EMD GP35s were in a state of disrepair. The MIRC rebuilt eight of the EMD GP35s for service. Additionally, the MIRC also operated three ALCO S-3s, two ALCO RS-1s, and two ALCO RS-2s.
Railroads in italics meet the revenue specifications for Class I status, but are not technically Class I railroads due to being passenger-only railroads with no freight component.