The Duluth, South Shore and Atlantic Railway (DSS&A; reporting mark DSA) was an American railroad serving the Upper Peninsula of Michigan and the Lake Superior shoreline of Wisconsin.

The development in the 1850s of hematite iron ore mines in the Upper Peninsula hills above Marquette encouraged the development of numerous railroad plans for spur lines and connecting routes between mines, local boom towns, and the shores of the Great Lakes.

While most of the Upper Peninsula's iron ore and Keweenaw copper was shipped to the rest of the United States by lake boat, the inability of water-based shippers to offer service to northern Michigan in winter encouraged railroad promoters to launch numerous plans for lines in the Upper Peninsula.

The Canadian Pacific Railway (CPR), a transcontinental line, took control of the Duluth, South Shore & Atlantic in 1888.

During the 1890s, the timber industry reached the peak of its operations on the Lake Superior shoreline properties adjacent to the DSS&A's new mainline, shipping old-growth white pine.

After white pines were exhausted, local cutters began to turn to high-quality hardwoods such as sugar maple, and then to pulpwoods such as paper birch and aspen.

Its story from 1920 onwards was that of the American railway industry as a whole, with negative factors intensified by unfavorable local business conditions in northern Michigan.

[4] The DSS&A's thinly settled service area made it difficult for the railroad to raise adequate revenue to maintain its trackage in good condition, especially in winter.