CINCINNATI -- When the Reds made plans to use the 2019 season to celebrate their 150th anniversary as baseball’s first professional team, the front office thought big.

And when a rare Friday off-day was on the schedule -- and during the Fourth of July weekend, no less -- Reds chief operating officer Phil Castellini saw a special opportunity. On July 5, at Great American Ball Park, the club will hold what it is calling “The Reds Rockin’ 150.”

“We wanted to celebrate it all year long,” Castellini said. “We wanted to reinvest in the Reds Hall of Fame. We wanted to have the leave-behind marker for the original 1869 team which we did with the pavilion and gazebo. We wanted to celebrate through the [15 throwback] uniforms and be able to tell that story and history in little chunks along the way.

“You have to have one big party, right? This is the manifestation of that.”

Being held from 5-10:30 p.m. ET, the event is free to the public but requires a ticket. The roughly 39,000 tickets sold out online, but a limited number of tickets will be made available on a first-come, first-served basis on event day at the main ticket windows beginning at 2 p.m.

What will this event look like?

“It’s like Redsfest meets Kids Opening Day, but here at the ballpark,” Castellini said. “And throw in a postgame concert-type format with a Rozzi’s fireworks show. All four components are coming together for what we’re calling the Rockin’ 150.”

The party will give fans an “open house” feel to GABP. They will be able to run the bases and walk along the warning track. There will be access to the diamond club section behind home plate, the press box and the Handlebar Club. Fans can take photos on the FOX Sports Ohio set. In the outfield, there will be Vietnam War-era Huey helicopters from the American Huey Museum in Indiana.

“We’re giving you the ability to see the ballpark in ways, maybe, that you never have,” Castellini said.

From 5:30-8 p.m., Reds players and coaches will be stationed at 11 spots around the ballpark to pose for photos with fans (no autographs, however). All four Reds mascots will also be available for photos.

At 8 p.m., on a stage built near second base, will be the main concert featuring 3 Doors Down, X Ambassadors and Phillip Phillips. Before the show, there will be more live music played on two side stages around the ballpark. The Bronson Arroyo Band, featuring the former Reds pitcher, will be among the performers.

A fireworks show -- similar to those seen following Friday home games -- will cap off the festivities.

Food at the concession stands will be sold at half price, and parking in the Hamilton County garages will cost $5. All tickets for the Reds Rockin' 150 will be delivered digitally via the free MLB Ballpark app to be scanned directly from smartphones at the event.

This party is happening, rain or shine.

When the Reds hosted the 2015 All-Star Game, the club was thinking ahead to ‘19 and its 150th season. The All-Star Gala, held at Union Terminal, was an original model of what Castellini initially envisioned. But it morphed into more of a community-based idea once internally called “The Great American Cookout.”

“We thought the format was cool and wanted to go down the road and, ‘Hey, we’ll have a big gala event.’ That model would have been really expensive, and I would have to charge people like $500 per couple to have some red-carpet, fancy thing. Only one-half of one percent of Reds fans would be able to go to it,” Castellini said. “We said that’s not what we want to do with this kind of anniversary for all of Reds fans. It’s how it evolved into the open-house event in the form we’re about to do on July 5.”