“Experience today what people will be talking about tomorrow.” That has become the mantra of the Museum of Contemporary Art Chicago as it prepares to celebrate its 50th anniversary, and pursue its ever-evolving role as a showcase for all that is new and provocative in the fields of both the visual and performing arts. And while a round-the-clock roster of special events is slated for the weekend of Oct. 21-22, preparations for the anniversary are already well underway. Originally the brainchild of a group of collectors, art dealers, artists, art critics and architects — who valued the venerable and internationally acclaimed collection of the Art Institute of Chicago, yet felt a powerful need for this city to also have a museum devoted to the creative spirit of the moment — the MCA has grown into one of the most prestigious cultural institutions of its kind in the country, standing alongside the Walker Art Center in Minneapolis, the Hammer Museum in Los Angeles,  Mass MOCA and a handful of others. The idea for such a contemporary art showcase was first formulated in 1964, at the very moment when this country was undergoing a monumental shift in its social, political and cultural nature. Three years later it opened its doors in a small building at 237 E. Ontario, where, as Madeleine Grynsztejn, who has served as the MCA’s director since 2008, proudly notes: “The very first event to be staged there was a Happening that involved composer John Cage and two founders of the Fluxus movement. And that tradition of combining the visual and performative arts has remained a major element of our programming ever since.” Artist Christo (bottom, foreground, with his team) goes about his work of wrapping the Museum of Contemporary Art with 10,000 square feet of tarpoline in 1969. | Bob Black/Sun-Times/File From the start the museum was on the cutting edge, with exhibits of the work of Claes Oldenburg and such other Pop Art icons as Andy Warhol, Roy Lichtenstein and Robert Rauschenberg. In 1969 its building became the site of Christo’s first “wrap” in the United States, and was encased in tarpaulin and rope. The MCA also was the first U.S. museum to mount solo exhibitions of