PS21 was founded by the late Judy Grunberg in 1999 with the mission of presenting advanced and diverse performances of music, dance, and theater, as well as some film screenings. Under her leadership as President of the Board, local residents and some from further away enjoyed lively summer programs performed in an ingenious plastic stage-cum-shelter in the middle of a field. Before her passing in 2019, she initiated the construction of an equally ingenious and certainly more elegant permanent structure which could be used from autumn through spring. A 300-seat theater open on three sides functions as the summer venue. Its stage house can be converted into a black box theater seating 99, providing a more intimate space for performances that need it. It was designed by a local architect, Evan Stoller, son of the legendary architectural photographer, Ezra Stoller.