Grant Park Concerts) is an annual 10-week classical music concert series, which features the Grant Park Symphony Orchestra and the Grant Park Chorus as well as guest performers and conductors. Since 2004, the festival has been housed in the Jay Pritzker Pavilion in Millennium Park. On occasion, the festival has been held at the Harris Theater instead of the Pritzker Pavilion. The festival has earned non-profit organization status, and claims to be the nation's only free, outdoor classical music series. The Grant Park Music Festival has been a Chicago tradition since 1931, when Chicago Mayor Anton Cermak suggested free concerts to lift spirits of Chicagoans during the Great Depression. The tradition of symphonic Grant Park Music Festival concerts began in 1935. The 2004 season, during which the festival moved to the Pritzker Pavilion, was the event's 70th season. Formerly, the Grant Park Music Festival was held at the Petrillo Music Shell in Grant Park. Over time the festival has had various financial supporters, three primary locations and one name change. At times it has been broadcast nationally on the National Broadcasting Corporation (NBC) and Columbia Broadcasting Service (CBS) radio networks, and many of the world's leading classical musicians have performed there. In 2000, the festival organizers agreed to release some of the concerts to the public via compact disc recordings. Installation of Burnham Pavilions in 2009 In 2009, architects Zaha Hadid and Ben van Berkel were invited to design and build two pavilions on the Chase Promenade South, to commemorate the 100th anniversary of Daniel Burnham's 1909 Plan of Chicago. The pavilions were privately funded and were designed to be temporary structures. They served as the focal point of Chicago's year-long celebration of Burnham's Plan, and were meant to symbolize the city's continued pursuit of the plan's architectural vision. The van Berkel Pavilion was composed of two parallel rectangular planes joined by curving scoops, all built on a steel frame covered with glossy white plywood. It was situated on a raised platform, which was sliced by a ramp entrance, making it ADA accessible. The Hadid Pavilion was a tensioned fabric shell fitted over a curving aluminum framework made of more than 7,000 pieces. A centennial-themed video presentation was projected on its interior fabric walls after dark. Both pavilions were scheduled to be unveiled on June 19, 2009. However, Hadid's pavilion was not ready in time; it had construction delays and