Answer:
Cohan's Little Johnny Jones
Cohan's Little Johnny Jones (1904) is considered the first American musical.
Explanation:
Although music has been a part of dramatic presentations since ancient times, modern Western musical theatre emerged during the 19th century, with many structural elements established by the works of Gilbert and Sullivan in Britain and those of Harrigan and Hart in America.
The Black Crook, the “First” Broadway Musical, Is Headed Back to NY. A tiny production of the massive spectacle will coincide with the show's 150th anniversary. On September 12, 1866, a happy accident occurred that changed Broadway forever.