Here’s a map of Duluth, via the great Perfect Duluth Day site, showing the city in 1887:
For Minnesota, Duluth is a really old city with Native American, fur trading, and lots of industrial history. By the 1880s, the recession of the 1870s was over and the city was booming again. According to Wikipedia:
In 1873, Jay Cooke’s empire crumbled and the stock market crashed, and Duluth almost disappeared from the map. But by the late 1870s, with the continued boom in lumber and mining and with the railroads completed, Duluth bloomed again. By the turn of the century, it had almost 100,000 inhabitants, and was again a thriving community with small-business loans, commerce and trade flowing through the city.
See also the Duluth population graph.