Janesville was the site of the first Wisconsin State Fair in 1851, attended by approximately 10,000 people.
R. Lavinia Goodell, Wisconsin's first female lawyer(1874), lived in Janesville.
A tree that once stood in downtown Courthouse Park was the site of a lynch mob that hanged a convicted murderer in 1859. In 1992, television journalist Geraldo Rivera was arrested for battery after an altercation during his coverage of a Ku Klux Klan rally in Janesville. The location of a related cross burning in 1992 is now "Peace Park" with a playground and a peace pole, said to be the world's tallest at 52 feet.
According to the United States Census Bureau, the city has a total area of 28.1 square miles (72.8 km²), of which, 27.5 square miles (71.3 km²) of it is land and 0.6 square miles (1.5 km²) of it (2.10%) is water. Janesville is divided by the Rock River.
Of the 23,894 households, 32.7% had children under the age of 18 living in them, 51.1% were married couples living together, 10.5% had a female householder with no husband present, and 34.1% were non-families. 27.4% of all households were made up of individuals, with 9.7% comprised of individuals aged 65 years or older. The average household size was 2.45 and the average family size was 2.99.
In the city, the population was spread out with 26.2% under the age of 18, 8.3% from 18 to 24, 31.2% from 25 to 44, 21.4% from 45 to 64, and 12.9% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 95.6 males. For every 100 females age 18 and over, there were 92.5 males.
The median income for a household in the city was $45,961, and the median income for a family was $55,133. Males had a median income of $40,910 versus $26,423 for females. The per capita income for the city was $22,224. About 4.3% of families and 6.5% of the population were below the poverty line, including 7.1% of those under age 18 and 5.8% of those age 65 and over.
Interstate 90/39 passes through Janesville, as do U.S. Hwy 14 and 51 and state Hwy 26 and 11. Just south of Janesville is Southern Wisconsin Regional Airport.
Janesville has two television stations licensed to the city; CW affiliate WBUW (Channel 57), which has its offices and transmitter in Madison and serves all of South Central Wisconsin, and W65EE (Channel 65), a low-power translator station of the Trinity Broadcasting Network. Many radio stations also serve Janesville.
Janesville has a public, internationally-themed botanical garden, Rotary Gardens, with free admission (donations accepted), that is open during the summer months. It is home to numerous weddings and group gatherings.
Traxler Park is home to the Rock Aqua Jays, a water ski team which has been U.S. national champion 15 times. The team originated and regularly hosts the National Show Ski championships. Traxler Park is also home to the Fourth of July festivities.
Other major parks include Riverside Park, a recreational park along the Rock River including a golf course and a segment of the Ice Age Trail; Rockport Park, largely undeveloped, including the municipal swimming pool and Peace Park; Monterey Park, including the Big Rock, an early natural landmark signalling a good ford of the Rock River (and the namesake of the county, but not the river), as well as a sports stadium used by the school system; Lustig Park, used for a disc golf course; and Palmer Park, which includes a 9-hole golf course and Camden Park (an accessible play area). Most of the parks in the city are linked by a paved bike trail, which will eventually connect to Beloit.
The Janesville School District has twelve elementary schools, three middle schools, two high schools and two charter schools. The Janesville Academy for International Studies, a charter high school that focuses on teaching global perspectives, and the Guide Language Center, which offers over 10 foreign languages, are both located downtown. In addition, there are a number of parochial schools throughout the city.
The Wisconsin School for the Visually Handicapped has been located in Janesville since 1850. A two-year community college, the University of Wisconsin-Rock County, located on the southwest side of Janesville, is part of the University of Wisconsin System. A two-year technical college, Blackhawk Technical College, is located midway between Janesville and Beloit; Blackhawk also offers degree programs through Upper Iowa University.
Regional employers include the non-profit Mercy Health System, which has a multi-county market extending into Illinois; Blain's Farm and Fleet, a three-state retail chain with headquarters and a distribution center in Janesville; and Woodman's Food Market, a regional supermarket chain, which built its first warehouse store in Janesville.
On June 3, 2008, General Motors announced plans to close the Janesville assembly plant as part of a significant restructuring effort. Begun in 1919, when General Motors bought the Janesville Machine Company and merged it with the Samson Tractor Company, the Janesville plant was the oldest General Motors plant in North America. It assembled large trucks and sport utility vehicles, which have declined in popularity as gasoline prices increased.
The Parker Pen Company was founded in Janesville; at one time its Main Street factory was the largest writing instrument plant in the world. The company later purchased Manpower, Inc., but eventually sold the pen business to Gillette and no longer operates in Janesville. It is now owned by the British company, Sanford. The Northwestern Mutual Life Insurance Company was founded in Janesville in 1857 but moved to Milwaukee two years later.
The Janesville Mall redeveloped in the late 1990s, and in 1998 Pine Tree Plaza opened. In November 2006, a Super Wal-Mart and a Sam's Club opened after a period of controversy. The site of the former Janesville Oasis, known for a large fiberglass cow at its entrance, began redevelopment in 2007; the anchor tenant will be a Super Menards and Bessie the cow, representing the local dairy industry, will be spared by popular demand.
The city is also home to many other Christian churches including Lutheran, Methodist, Episcopalian, Baptist, and others. The Seventh Day Baptist General Conference has its offices in Janesville; the denomination's nearest church is in Milton.
The Gideon Bible organization was founded at the Janesville YMCA in 1899 by Janesville resident John H. Nicholson and a Beloit man after they had shared a Boscobel hotel room.
In 1994, a white buffalo dubbed Miracle was born at the Heider family farm just outside Janesville. Miracle lived until 2004. She was frequently visited by Native American ceremonial groups because of sacred symbolism of white buffaloes in many Native American religions. Another unrelated white buffalo, named Miracle's Second Chance, was born at the same farm in 2006, but died in a lightning strike later that year.