The Detroit, Mackinac and Marquette Railroad was a land grant railroad that was built and operated briefly (1881-1886) in the Upper Peninsula of the U.S. state of Michigan. Incorporated in 1879, the 151.9-mile (244.5 km)-long railroad began operations in 1881. It was intended to help the economic development of a region of frontier timberland along the shores of Lake Michigan and Lake Superior. Its successor line was the Duluth, South Shore and Atlantic Railway.
The Detroit, Mackinac and Marquette (DM&M) Railroad was built in 1879-1881 by Detroit businessman James McMillan, Francis Palms, and their venture-capital partners. Unlike many U.S. railroads, the Detroit, Mackinac and Marquette was built from west to east. Its main line stretched from its namesake city, Marquette, Michigan, to the Straits of Mackinac at St. Ignace, Michigan. The railroad itself did not reach Detroit, but offered service thither through its part ownership of the Mackinac Transportation Company, a railroad car ferry service that shuttled railroad cars across the Straits of Mackinac to the DM&M's partner lines in Mackinaw City, Michigan.
Despite being the recipient of 1,327,042 acres (5,370.35 km2) of Upper Peninsula real estate, the Detroit, Mackinac and Marquette was not a financial success. It declared bankruptcy in summer 1886, and was allowed by its creditors to continue business under the temporary name of the Mackinaw and Marquette Railroad. In the foreclosure sale October 1886, the bankrupt railroad and its assets were sold to the McMillan family for $1.05 million. In December of the same year, the McMillan interests folded the Mackinaw and Marquette Railroad into the consolidated Duluth, South Shore and Atlantic Railway. The former DM&M main line became a key component of the new Upper Peninsula railroad.