The South Main Street Historic District a fairly intact remnant of Janesville, Wisconsin's old downtown east of the Rock River, built in the 19th and early 20th centuries.

In 1990 the district was added to the National Register of Historic Places.

[2] Commerce in Janesville began in Henry Janes' cabin, built in 1836, where the Lappin-Hayes block now stands at the intersection of East Milwaukee and Main Streets.

From that cabin Janes operated a rustic inn, general store, post office, and a ferry across the Rock River.

Many of the street-level storefronts have been extensively remodeled, but the upper stories often remain very much as built.