Chicago is an American rock band formed in 1967 in Chicago, Illinois as The Chicago Transit Authority before shortening the name in 1970. The self-described "rock and roll band with horns" began as a politically charged, sometimes experimental, rock band and later moved to a predominantly softer sound, generating several hit ballads. The group had a steady stream of hits throughout the 1970s and 1980s. Since at least 2008, Billboard has shown Chicago to be the "greatest of all time" American band in singles chart success, and since 2015, the "greatest of all time" American band in album chart success as well.

Upon being renamed from Chicago Transit Authority to Chicago, the band sported a new logo. Its inspiration was found in the design of the Coca-Cola logo, in the attitude of the city of Chicago itself, and in the desire to visually transcend the individual identities of the band's members. It was designed by the Art Director of Columbia/CBS Records, John Berg, with each album's graphic art work being done by Nick Fasciano. Berg said, "The Chicago logo...was fashioned for me by Nick Fasciano from my sketch."  The logo would serve as the band's chief visual icon from Chicago II, onward. In various artistic forms and visual similes, it has been the subject of every subsequent album cover, except the fifteenth album, Greatest Hits, Volume II. For example, it appeared as an American flag on III, a piece of wood on V, a U.S. dollar bill on VI, a leather relief on VII, an embroidered patch on VIII, a chocolate bar on X, a map on XI, a building on 13, a fingerprint on XIV, a computer silicon chip on 16, a parcel on 17, a mosaic on 18, and an aquarelle on 19. Chicago IX's incarnation was a caricature of the band itself, in the shape of the logo.  The album cover series has endured as a cataloged work of art in its own right, described by Paul Nini of the American Institute of Graphic Arts as a "real landmark in record cover design". In 2013, the iconic status of Chicago's album art was featured in a New York art museum exhibit, which centered upon ninety-five album covers completely selected from John Berg's career portfolio of hundreds. Having overseen the design of approximately fourteen Chicago album covers across more than twenty years, Berg stated that this artistic success resulted from the combination of Chicago's "unique situation" and his position in "the best possible job at the best possible time to have that job, at the center of the graphic universe". Berg won the 1976 Grammy Award for Best Album Package for Chicago X, one of four Grammy Awards he won in his lifetime.  The book titled Type and Image: The Language of Graphic Design described the logo as "a warm vernacular form, executed in thick script letters with Victorian swashes in the tradition of sports teams and orange crate labels." The book mentions the cultural and material background of the city of Chicago as inspiration for the logo; for example, describing the leather embossing of Chicago VII as representative of the great fire and the stockades. The author connects the album art to the atmosphere of the band's namesake city, quoting the band's original manager, James William Guercio: "The printed word can never aspire to document a truly musical experience, so if you must call them something, speak of the city where all save one were born; where all of them were schooled and bred, and where all of this incredible music went down barely noticed; call them CHICAGO."

why did they change their names
"The printed word can never aspire to document a truly musical experience, so if you must call them something, speak of the city where all save one were born;