"Saturday in the Park" was very successful upon release, reaching No. 3 on the Billboard Hot 100, becoming the band's highest-charting single at the time, helping lift the album to No. 1.Billboard ranked it as the No. 76 song for 1972. The single was certified Gold by the RIAA, selling over 1,000,000 units in the U.S. alone.
According to fellow Chicago member Walter Parazaider, Lamm was inspired to write the song during the recording of Chicago V in New York City on July 4, 1971 (actually a Sunday):
Robert came back to the hotel from Central Park very excited after seeing the steel drum players, singers, dancers, and jugglers. I said, 'Man, it's time to put music to this!
In the studio version of the song, the line "singing Italian songs" is followed by "Eh Cumpari" (the title of a song made famous by Julius La Rosa in 1953), and then Italian-sounding nonsense words, rendered in the printed lyrics as "?". Piano, guitar, and vocal sheet music arrangements have often read "improvised Italian lyrics" in parentheses after this line. However, in a film of Chicago performing "Saturday in the Park" at the Arie Crown Theater in Chicago in 1972, Robert Lamm clearly sings, "Eh Cumpari, ci vo sunari," the first line of "Eh, Cumpari!".