From Chicago, they formed in 1966, and went on to become one of the top selling acts of 1967, charting their only five Top 40 hits in the U.S. that year. The band dissolved in early 1970, but re-formed in 1980 and as of 2019 they continue to tour throughout the United States.
Released as a single in 1967, and on their album Portraits in 1968, Susan spent 12 weeks on the Billboard Hot 100 chart, peaking at No. 11.
https://youtu.be/bAHlAnAXDJIMost radio stations played an edited version of the record which left out the psychedelic portion of the song (1:36 - 2:05). Some claim that there were spoken drug references in that section as well. That excerpt was a portion of Charles Ives'
Central Park in the Dark (1905)...
https://youtu.be/RC6jSHYQURcI hear the sound of a train pulling out of a station toward the end of the excerpt.