Written and first recorded by Simon & Garfunkel (1966).
Hit version by Harpers Bizarre (US #13 1967).
From the wiki: “‘The 59th Street Bridge Song (Feelin’ Groovy)’ was written by Paul Simon and first recorded by Simon & Garfunkel, appearing on their 1966 album Parsley, Sage, Rosemary and Thyme. ’59th Street Bridge’ is the colloquial name of the Queensboro Bridge in New York City. The most popular cover version of the song was recorded in 1967 by Harpers Bizarre, reaching #13 on the Billboard Hot 100.
“Paul Simon would later allege that the theme song to the children’s television program H.R. Pufnstuf too closely mimicked ‘The 59th Street Bridge Song’. Simon successfully sued and his name was added as a writing credit.”
Harpers Bizarre, “59th Street Bridge Song (Feelin’ Groovy)” (1967):
H.R. Pufnstuf theme song (1969):