The Monkees' debut single, "Last Train to Clarksville," written and produced by Tommy Boyce and Bobby Hart, hit #1 on the Billboard Hot 100 on November 5, 1966.
Monkees archivist Andrew Sandoval wrote about the July 25, 1966 session at RCA Hollywood for the song (which also included work on the first version of "I Can't Get Her Off My Mind") in his book, The Monkees: The Day-by-Day Story of the '60s TV Pop Sensation:
This ad for the single appeared in the September 3, 1966 issue of Billboard (courtesy of Monkee45s.net):
Here's video footage of all four Monkees performing "Last Train to Clarksville" live at Wembley in London, England in March 1997:
The single's B-side was the stellar Gerry Goffin & Carole King track "Take a Giant Step":