How did Chicago (band) get their name?

The original band membership consisted of saxophonist Walter Parazaider, guitarist Terry Kath, drummer Danny Seraphine, trombonist James Pankow, trumpet player Lee Loughnane, and keyboardist/singer Robert Lamm. The group of six called themselves "The Big Thing". Realizing the need for both a tenor to complement baritones Lamm and Kath, and a bass player because Lamm's use of organ bass pedals did not provide "adequate bass sound", they added local tenor and bassist Peter Cetera.

In June 1968, at manager James William Guercio's request, The Big Thing moved to Los Angeles, California, and signed with Columbia Records. The band changed its name to "Chicago Transit Authority".

After the release of their first album, the band's name was shortened to Chicago to avoid legal action being threatened by the actual mass-transit company of the same name.