From Wikipedia:
"Goodnight, Ladies" is a folk song attributed to Edwin Pearce Christy, originally intended to be sung during a minstrel show. Drawing from an 1847 song by Christy entitled "Farewell, Ladies", the song as known today was first published on May 16, 1867.
The "Merrily We Roll Along" chorus has the same melody as "Mary Had A Little Lamb".
Meredith Willson features the piece as the tenth number in The Music Man (1957).
John