city, seat (1839) of Rock county, southern Wisconsin, U.S. It lies on the Rock River, about 15 miles (25 km) north of Beloit and 40 miles (65 km) southeast of Madison. Settled in 1835 and named for a pioneer, Henry F. Janes, it developed as a trading centre for the surrounding agricultural region and as a manufacturing (agricultural equipment and writing instruments and later automobiles) and milling (lumber, flour, wool) centre. Automobile manufacturing is the basis of the modern economy; other products include automotive parts, machinery, plastics, textiles, electrical products, and room partitions. The city is also part of a major agricultural area, with crops that include soybeans, corn (maize), and tobacco.

The city is the seat of the two-year University of Wisconsin (Wisconsin, University of)–Rock County (1966) and Blackhawk Technical College (1968); the Wisconsin Center for the Blind and Visually Impaired and the Wisconsin School for the Visually Handicapped are also in the city. The Lincoln-Tallman Restorations include a mansion (c. 1855) where Abraham Lincoln (Lincoln, Abraham) once spent the night. A portion of Ice Age National Scenic Trail passes through the city. The nearby Milton House (1844), a national historic landmark, was a station on the Underground Railroad for runaway slaves and has been preserved as a museum. Because Janesville has some 2,000 acres (800 hectares) of parkland, it has been given the nickname “Wisconsin's Park Place.” The city was the birthplace (1862) of Carrie Jacobs Bond (Bond, Carrie Jacobs), a composer of sentimental songs, and it was where she wrote one of her most popular songs, "I Love You Truly." Inc. 1853. Pop. (1990) city, 52,133; Janesville-Beloit MSA, 139,510; (2000) city, 59,498; Janesville-Beloit MSA, 152,307.