Chicago (retroactively known as Chicago II) is the second studio album by the American rock band Chicago, released on January 26, 1970, by Columbia Records. Like their debut album, Chicago Transit Authority (1969), it is a double album. It was their first album released under the name Chicago—the band's prior name, Chicago Transit Authority, was changed due to a threatened lawsuit from the actual mass-transit operator of the same name—and the first to use the now ubiquitous cursive Chicago logo on the cover.
Chicago was commercially successful. It reached No. 4 on the US Billboard 200 and No. 6 on the UK Albums Chart, and produced three top ten singles on the Billboard Hot 100. It was certified Gold by the Recording Industry Association of America (RIAA) in April of the same year of its release, and certified Platinum in 1991. The album received three Grammy Award nominations at the 1971 Grammy Awards: Album of the Year, Best Contemporary Vocal Performance by a Duo, Group or Chorus, and Best Album Cover. It was voted the best album of 1970 by readers of Cash Box magazine, and the 1971 best small-combo LP by readers of Playboy magazine.