Twenty years ago, at the 1993 Whitney Biennial, fault lines opened up and the ground shifted. About 30 of the 43 artists were in the museum for the first time. More than 40 percent of the participants were women, quite a few were nonwhite, and a generous amount of the work was about being openly gay. One of the exhibition’s admission buttons, designed by artist Daniel J. Martinez, read I CAN’T IMAGINE EVER WANTING TO BE WHITE. People went batshit.