Allen RuckerIf you want to know where disability has made the biggest impact in any form of American media, check out the live theater listings in New York City, Chicago, Cleveland, Seattle and maybe your town, too. Long a fountainhead of innovation and inspiration for film and television, the “thea-taa” — actors, playwrights, musical dramatists and the impresarios who pay for it all — has gradually been introducing characters and plot lines featuring disability experiences since The Miracle Worker first opened on Broadway in 1959. Just in the last two to three years, though, the pace has greatly accelerated. Performers with disabilities have gone from cast members