[1] In 1986, 6th Street was closed and Kiener Plaza was extended west with the Morton D. May Amphitheater, designed as a postmodern Roman ruin with a capacity for about 500 people.

[3][4] Improvements proposed in the 2009 Gateway Mall Master Plan included an event lawn, a performance pavilion and plaza, new lighting, and bringing the sunken portion of the park up to street level.

[6] It reopened on May 19, 2017 and saw the sunken amphitheater replaced with street level open spaces, a playground, a water feature, and a lawn that can accommodate up to 3,000 people.

[6] The plaza is named for Harry Kiener, a local philanthropist and member of the U.S. track team at the 1904 Olympics held in St. Louis.

[7] Because of its central location within downtown St. Louis, the plaza is often host to public events including outdoor free movies and a winter festival.