Mayor Henry Kiel, attorney Guy Golterman, and Parks Commissioner Nelson Cunliff stepped in and, in 49 days (not counting seven lost to rain), created the first municipally owned outdoor theatre in the United States.

The first show under the Muny banner was Robin Hood, which opened on June 16, 1919, and featured Mayor Kiel as King Richard.

Improvements for 1922 included a new pergola, 750 permanent opera chairs, 500 parking spaces for automobiles, and the addition of "comfort stations".

Additions for 1923 included 1,800 permanent seats, an extra stage for rehearsals, and a sound amplifier to enable people in the back of the audience to hear as well as those in the front.

[5] On January 4, 1923, the Municipal Theater Association opened a free school for people who aspired to sing in the chorus for that summer's productions.

[6] Keil stepped down from being president of the Municipal Theater Association in 1924, saying that the enterprise should be headed by businessmen, and Cunliff simultaneously left his position as chairman of the group's Executive Productions Committee.

Other notable artists who have performed on the Muny stage include Whitney Houston, Patti LaBelle, Sting, Barry Manilow, Bob Dylan, Allman Brothers, Hank Williams Jr., The Beach Boys, and James Taylor.

In 2024, The Muny revived the tradition and presented its first live concert in more than 30 years — a one-night-only show starring Emmy, Grammy, Oscar and Tony winner John Legend accompanied by the St. Louis Symphony Orchestra.

“Generations of St. Louisans have memories of seeing legendary music acts on our magnificent stage, and I am excited to deliver this bit of nostalgia to our community at the end of our 2024 summer season.” [12]