Champaign not only shares a border with the neighboring city of Urbana, but together they are home to the University of Illinois. They are sometimes colloquially referred to as the "Twin Cities" or Chambana.

Champaign was founded in 1855, when the Illinois Central Railroad laid its rail track two miles west of downtown Urbana. Originally called "West Urbana", it was renamed Champaign when it acquired a city charter in 1860.

Spray whipped cream or "Instantwhip" was invented in Champaign during the depression by Charles Getz, a graduate student in the Chemistry Department at the University of Illinois, who found that milk would foam if pressurized nitrous oxide was forced into it. Professor G. Frederick Smith would later use Getz's patented method to create Instantwhip Foods.

In 1969, Carl Perkins teamed up with Bob Dylan to write "Champaign, Illinois", which Perkins released on his album On Top. The band Old 97's took another Bob Dylan song, "Desolation Row", and combined its melody with new lyrics to make a second song called "Champaign, Illinois", which they released with Dylan's blessing on their 2010 album The Grand Theatre Volume One. The two "Champaign, Illinois" songs are not related except for the fact that Bob Dylan was involved in both of them.

Champaign has a total area of 22.457 square miles (58.16 km²), of which 22.43 square miles (58.09 km²) or 99.88% is land and 0.027 square miles (0.07 km²) or 0.12% is water.

The record high temperature in Champaign was 109 °F (42.8 °C), recorded in 1954, and the record low was -25 °F (-31.7 °C), recorded on four separate occasions in 1899, 1905, 1994 and 1999.

In 1948, Champaign's University of Illinois became the first college in the United States to establish a collegiate wheelchair basketball team. The move was a huge success, and wheelchair basketball quickly became the number one sport of individuals with disabilities.

In 1966, Neal Doughty entered the electrical engineering program at the University of Illinois. On his first night, he met fellow student Alan Gratzer. They held an impromptu jam session in the basement of their Illinois Street Residence Hall dormitory and soon started REO Speedwagon, which cultivated a following during the 1970s and achieved significant commercial success throughout the 1980s. The group's best-selling album, Hi Infidelity (1980), contained four US top 40 hits and sold more than 10 million copies.

The Virginia Theatre has been providing theatrical and cinematic entertainment to the Champaign-Urbana community since its doors first opened in 1921. It was added to the National Register of Historic Places in 2003.

Film critic Roger Ebert did more than just review movies. One of his many triumphs was the founding of "Ebertfest", an annual film festival for overlooked movies that takes place in Champaign, Illinois. After his death, a life-size bronzed statue of Ebert sitting on a bench giving his famous thumbs up was installed outside Champaign's Virginia Theater. The sculpture's title is "C-U at the movies," after his signature sign-off.