Question: Where did the third collaboration open by Richard Rodgers  and Oscar Hammerstein II , The form began to flourish in the late 1960s?

Context paragraphs:
Cinderella (2013 cast album): Rodgers + Hammerstein's Cinderella is an original cast album of the first Broadway production of the musical "Cinderella", with music by Richard Rodgers, lyrics by Oscar Hammerstein II and a book by Douglas Carter Beane based partly on Hammerstein's 1957 book.  The story is based upon the fairy tale Cinderella, particularly the French version "Cendrillon, ou la Petite Pantoufle de Vair", by Charles Perrault.  The production opened in 2013.  In Beane's plot, Cinderella opens Prince Topher's eyes to the injustice in the kingdom.

Allegro (musical): Allegro is a musical by Richard Rodgers (music) and Oscar Hammerstein II (book and lyrics), their third collaboration for the stage.  Opening on Broadway on October 10, 1947, the musical centers on the life of Joseph Taylor, Jr., who follows in the footsteps of his father as a doctor, but is tempted by fortune and fame at a big-city hospital.

South Pacific (musical): South Pacific is a musical composed by Richard Rodgers, with lyrics by Oscar Hammerstein II and book by Hammerstein and Joshua Logan.  The work premiered in 1949 on Broadway and was an immediate hit, running for 1,925 performances.  The plot of the musical is based on James A. Michener's Pulitzer Prize-winning 1947 book "Tales of the South Pacific" and combines elements of several of those stories.  Rodgers and Hammerstein believed they could write a musical based on Michener's work that would be financially successful and, at the same time, would send a strong progressive message on racism.

Rodgers and Hammerstein: Rodgers and Hammerstein refers to composer Richard Rodgers (1902–1979) and lyricist-dramatist Oscar Hammerstein II (1895–1960), who together were an influential, innovative and successful American musical theatre writing team.  They created a string of popular Broadway musicals in the 1940s and 1950s, initiating what is considered the "golden age" of musical theatre.  Five of their Broadway shows, "Oklahoma! ", "Carousel", "South Pacific", "The King and I" and "The Sound of Music", were outstanding successes, as was the television broadcast of "Cinderella".  Of the other four that the team produced on Broadway during their lifetimes, "Flower Drum Song" was well-received, and none was an outright flop.  Most of their shows have received frequent revivals around the world, both professional and amateur.  Among the many accolades their shows (and film versions) garnered were thirty-four Tony Awards, fifteen Academy Awards, the Pulitzer Prize, and two Grammy Awards.

Cinderella (musical): Rodgers and Hammerstein's Cinderella is a musical written for television, with music by Richard Rodgers and a book and lyrics by Oscar Hammerstein II.  It is based upon the fairy tale Cinderella, particularly the French version "Cendrillon, ou la Petite Pantoufle de Verre", by Charles Perrault.  The story concerns a young woman forced into a life of servitude by her cruel stepmother and self-centered stepsisters, who dreams of a better life.  With the help of her Fairy Godmother, Cinderella is transformed into a Princess and finds her Prince.

Concept musical: Concept musicals were first introduced in the 1940s, though two shows compete for the title of 'first concept musical:' "Allegro" and "Love Life".  The form began to flourish in the late 1960s, with the advent and subsequent popularity of "Man of La Mancha", "Cabaret", and "Hair".  Stephen Sondheim, the most prolific author of concept musicals, created "Company" in 1970, bringing the genre to the forefront of the commercial realm.  Director-choreographer Bob Fosse and producer-director Harold Prince were equally instrumental in making defining contributions to the concept musical.  Modern examples of the concept musical include "Assassins" and "Avenue Q".  Shows ranging from "Fiddler on the Roof" to "Sweeney Todd" have been argued as being concept musicals, though there is little critical agreement.

Oscar Hammerstein II: Oscar Greeley Clendenning Hammerstein II ( ; July 12, 1895 – August 23, 1960) was an American librettist, theatrical producer, and (usually uncredited) theatre director of musicals for almost forty years.  Hammerstein won eight Tony Awards and two Academy Awards for Best Original Song.  Many of his songs are standard repertoire for vocalist's and jazz musicians.  He co-wrote 850 songs.  Hammerstein was the lyricist and playwright in his partnerships; his collaborators wrote the music.  Hammerstein collaborated with numerous composers, such as Jerome Kern, with whom he wrote "Show Boat", Vincent Youmans, Rudolf Friml, Richard A. Whiting and Sigmund Romberg; but he is best known for his collaborations with Richard Rodgers, as the duo Rodgers and Hammerstein which include "Oklahoma! ", "Carousel", "South Pacific", "The King and I", and "The Sound of Music".

Cinderella (2013 Broadway production): Rodgers + Hammerstein's Cinderella is a musical in two acts with music by Richard Rodgers, lyrics by Oscar Hammerstein II and a book by Douglas Carter Beane based partly on Hammerstein's 1957 book.  The story is based upon the fairy tale "Cinderella", particularly the French version "Cendrillon, ou la Petite Pantoufle de Verre", by Charles Perrault.  The story concerns a young woman forced into a life of servitude by her cruel stepmother, who dreams of a better life.  With the help of her Fairy Godmother, Cinderella is transformed into an elegant young lady and is able to attend the ball to meet her Prince, but, in this version, she must open the Prince's eyes to the injustice in his kingdom.

Carousel (musical): Carousel is the second musical by the team of Richard Rodgers (music) and Oscar Hammerstein II (book and lyrics).  The 1945 work was adapted from Ferenc Molnár's 1909 play "Liliom", transplanting its Budapest setting to the Maine coastline.  The story revolves around carousel barker Billy Bigelow, whose romance with millworker Julie Jordan comes at the price of both their jobs.  He attempts a robbery to provide for Julie and their unborn child; after it goes wrong, he is given a chance to make things right.  A secondary plot line deals with millworker Carrie Pipperidge and her romance with ambitious fisherman Enoch Snow.  The show includes the well-known songs "If I Loved You", "June Is Bustin' Out All Over" and "You'll Never Walk Alone".  Richard Rodgers later wrote that "Carousel" was his favorite of all his musicals.

Pipe Dream (musical): Pipe Dream is the seventh musical by the team of Richard Rodgers and Oscar Hammerstein II; it premiered on Broadway on November 30, 1955.  The work is based on John Steinbeck's short novel "Sweet Thursday"—Steinbeck wrote the novel, a sequel to "Cannery Row", in the hope of having it adapted into a musical.  Set in Monterey, California, the musical tells the story of the romance between Doc, a marine biologist, and Suzy, who in the novel is a prostitute; her profession is only alluded to in the stage work.  "Pipe Dream" was a flop and a financial disaster for Rodgers and Hammerstein.

Supporting paragraphs: Concept musical Allegro (musical)
Answer: Broadway