Interstate 39, Interstate 90, and U.S. 51 pass through Janesville.
As of the 2010 census, the city had a population of 63,575. The Janesville area was home to many Native American tribes before the settlement of people from the East. With the Indian Removal Act of 1830, many Native American peoples were uprooted and forced out of their homelands to make room for the new settlers, with many Native peoples, including the Ho-Chunk and Potawatomi, being forced onto reservations. American settlers John Inman, George Follmer, Joshua Holmes, and William Holmes, Jr. built a crude log cabin in the region in 1835. Later that year, one key settler named Henry Janes, a native of Virginia who was a self-proclaimed woodsman and early city planner, arrived in what is now Rock County. Janes came to the area in the early 1830s, and initially wanted to name the budding village “Blackhawk," after the famous Sauk leader, Chief Black Hawk, but was turned down by Post Office officials.