“Gun one, ready … fire!”

Children’s hands jump to cover their ears as a cannon blasts out a gigantic “boom.” An infant bursts into tears. Adults wince.

But the report, loud enough to set off a few car alarms, doesn’t seem to phase 12-year-old Jack Robertson, who in his leather boots, blue wool uniform and kepi, looks every bit the part of the Civil War-era powder monkey he is portraying.

“It’s not so bad,” the Lawrence boy says of the cannon’s call.

Others seemed to agree, judging by the crowds that gathered Saturday afternoon in Constant Park to watch and listen as Civil War re-enactors in period garb loaded and fired three of the weapons.

The artillery camp and firing were part of activities associated with the seventh annual Civil War on the Western Frontier, a living history event that focuses on historic Lawrence during early territorial days and the Civil War. Festivities began Aug. 11 and will end Aug. 25 Â four days after the 139th anniversary of Quantrill’s Raid.

Robertson’s job as powder monkey is to fetch a round of black cannon powder, put it into a leather bag and wait for a Union soldier to call out, “Advance the round.”

“Then I take it up,” he said, chomping on an apple during a break between firings. “I’ve always wanted to do it, but I just turned old enough.”

Other children were less envious of Robertson’s chore.

“It would be a little too loud for me,” said 7-year-old Avi Whitten-Vile, who went to the park with his sister and father to figure out what all the ruckus was about.

“First, we thought it was thunder,” Avi’s father, Sheldon Whitten-Vile, said. “Then we figured it sounded a little bit different.”

Between firings, families moseyed around the encampment’s A-frame canvas tents, questioned soldiers about their uniforms and weapons and laughed as children fought for turns working a water pump, one of several examples of items used during the Civil War era.

“If they had to fill the bath tub with it, I don’t think they’d be so thrilled,” joked Dorothy Curnes of Lawrence. Her blond-headed, 4-year-old granddaughter, Hannah Weissbeck of Overland Park, smiled with wonder as more water spilled out of the pump spout with each new crank of her arm.

Off behind the tents, two boys, one in period costume, ran among the trees, aiming toy pistols at each other and shrieking, “Bang. Boom. Gotcha. You’re dead.”

Near the campfire, a huddle of soldiers and civilians sat conversing about what appeared from their intent expressions to be serious war matters. A closer listen revealed the true topic: e-mail.

But the devoted infantrymen were quick to spring back into character.

Clearing his throat, one man said, “We were discussing the telegraph.”