"It was tarps all over the place," said Commander's daughter, Elizabeth, 20.
"We love the history. We love the music. We're suckers for free concerts," Barbara Commander said.
Saturday's was the 18th annual Salute to Independence, performed by the Maryland Symphony Orchestra. Ron Maxwell, director of the Civil War film "Gods and Generals," and film score composer John Frizzell also hosted the event.
The sun blazed before the show began, but concert-goers came prepared.
"Heat was the issue this year," said park superintendent John Howard. "But people pretty much took care of themselves."
He said the heat kept the crowds at bay, with an estimated 25,000 attendees this year, about 5,000 fewer than last year.
Howard said there were three reports of people overcome by heat, but they were treated on site and not taken to the hospital.
Donnie Waybright, 46, of Hagerstown, and his family were among the attendees. Waybright's arms and shoulders were pink with sunburn.
"I didn't really burn. ... I'll be fine tomorrow," he said.
Janet Harkness, 42, of Calvert County, Md., was sitting beneath a tent with family and friends. Her group - 22 children and six adults - had brought three coolers of food and snacks, board games, cards, books and balls to keep entertained.
Having been at the battlefield since about 1:30 p.m., Harkness said they brought "lots of water" and sunscreen, which she deemed "a must."
Harkness said her family's packing was also in preparation for the long wait to leave the battlefield once the show was over.
"We just wait for the crowd to get out," she said.
Once the concert got under way, people said they enjoyed the show, which included the first public performance of music from the "Gods and Generals" soundtrack.
Rolf Schmitt, 52, of Baltimore, who was wearing a Civil War battle cap, at the show, said the music was a nice touch.
"It was appropriate. A nice addition to the program," Schmitt said.
The movie was filmed in part in Washington County.
Schmitt said he was glad to see the cannons would complement the "1812 Overture" again this year; the Maryland National Guard unit that usually performs had been called to duty last year.
Jane Van Norstrand, 47, of Duluth, Minn., was visiting family in Maryland with her daughter, Suanna, 15. Van Norstrand, who has seen both of Maxwell's Civil War films - "Gettysburg" and "Gods and Generals" - said the concert tied the history together for her.
"I like the fact that it was narrated. ... I think it really adds a lot of flavor ... and maybe a little closer with what they did here, the battles."
After the sun went down and the music ended, the fireworks began, illuminating the battlefield and the masses as they watched.
"They're great," said Melissa Medina, 18, of Greencastle, Pa. "This is my first time being here, and I didn't expect this many people. ... This is like billions of people. I'm afraid I'm going to get lost."
Frank Paternoster, 33, and his son, Brandon, 11, were watching the fireworks together.
"It's pretty cool," Brandon said. "Is this the best part? Yeah. I think it is."