Streisand recorded three songs with Columbia Records’ pop arranger Jimmy Wisner (the other two were “Our Corner of the Night” and “He Could Show Me”)—and “Frank Mills” was the third.

“Frank Mills” was a comedy song from the Broadway musical Hair which was a huge hit in 1968. After an off-Broadway debut on October 17, 1967, at Joseph Papp's Public Theater and a subsequent run at the Cheetah nightclub from December 1967 through January 1968, the show opened on Broadway in April 1968 and ran for 1,750 performances. 

The New York Times wrote in 2007 complimentarily about the song:

“Frank Mills” ... is a beautifully distilled portrait of the times seen from the perspective of a young girl looking for a guy she has fallen for instantly. An unusual pop song with no verse, no chorus and no rhymes, it is a plaintive little monologue with charming anecdotal lyrics that ride gently on Mr. MacDermot’s similarly meandering melody ...

It took Streisand and Columbia Records nearly a year to release her recording of the song.  Of course, the hype around Hair had faded by that time.  And seven other singers on different labels had recorded “Frank Mills” by then:  Jean Livingston, Liza Minnelli, Phyllis Newman and Shelley Plimpton among them.

“Frank Mills” has never appeared on a Barbra Streisand album and, to date, has only been released as a vinyl 7-inch single.

The b/s of the single was Paul Simon's song, “Punky's Dilemma,” which appeared on Barbra's album What About Today? “Punky's Dilemma” was written for Mike Nichols’ film The Graduate but was unused. It ended up on the Simon & Garfunkel album Bookends.