Metro Parks will celebrate 75 years of outdoor entertainment at the Iroquois Amphitheater Sunday with live music from the Louisville Big Band Jazz Ensemble, dancing and a concert by South Louisville native Justin Paul Lewis. Gates open at 5 p.m. for this free event.The parks department invites anyone who has ever performed on stage or worked backstage at the amphitheater to gather at 7:30 p.m. for a group photo on stage.“We really want to put the call out there as widely as possible to anybody and everybody who has ever performed on or backstage at the amphitheater to join us for this one-of-a-kind group photo,” says amphitheater manager Mike Slaton.Sunday’s event caps off a weekend of free season-closing events. The Louisville Vocal Project and Bellarmine University Music Department perform Friday (7:30 p.m.), and Saturday’s percussion festival features River City Drum Corps and the Louisville Leopard Percussionists (4-7 p.m.).When the amphitheater was built in 1938 as a Works Progress Administration project, construction took only 75 days. The outdoor venue hosted touring operettas and musicals in its heyday.“With the rise of air conditioning and television it went into decline, and has been in periods of decline and rebirth in the Fifties, Sixties and Seventies,” says Slaton. “There was a big resurgence in the Eighties with Music Theatre [of Louisville] out here. Then we had a ten-million dollar renovation that was completed in 2004 that brought us into this new phase of being a multi-use venue.”Now, the venue hosts 50-60 performing arts events every year. Programming ranges from the Iroquois Amphitheater Presents Series, which stages its own musical productions (“Once Upon a Mattress,” 2011; “H.M.S. Pinafore,” 2012; “Pirates of Penzance,” 2013), to hosting popular touring musical acts like The National, Edward Sharpe and the Magnetic Zeroes and The Black Keys. The amphitheater also partners with local arts organizations like the University of Louisville Dance Theatre to present free or low-cost arts events.“We’ve had a lot of support from the [Metro] Council folks, including Marianne Butler, whose district includes Iroquois Park,” says Slaton. “She’s been a huge supporter of the amphitheater and has helped make us a success over the last couple of years.”The official season might be coming to a close, but entertainment at Iroquois Park continues into the fall and winter. The amphitheater has expanded programming year-round by turning the stage itself into a black box theater space dubbed Parkside Studio in the off-season. And the Jack o’Lantern Spectacular opens in October 10 and runs through November 2. Five thousand carved pumpkins lining a quarter-mile walking trail in the park will be illuminated every night from dusk until midnight on the weekdays and 1 a.m. on weekends.