You have to use your imagination. The ruins are all gone — the aftermath was all about quick rebuilding, no defeatism allowed — but the legacy lives on, right here on Massachusetts Street.

Imagine South Park as a cornfield, New Hampshire Street as a dirt road, horses hitched up at Eighth Street, and the arts center as a camp for Union recruits, some as young as 16. Picture the Dusty Bookshelf as a fledgling public library — there’s no librarian yet, but there will be, especially when 85 newly made widows will need to find work to feed their families.

Watson Park is a ravine. In the midst of four hours of terror, many people will hide there. On that Friday in 1863, what’s now known as the “train park” will be where the survivors lay the bodies.

Lawrence is a 9-year-old town in a 2-year-old state. The nation is at war, and at about 5 a.m. Aug. 21, a former resident of Stone’s Hotel at Sixth and New Hampshire will lead nearly 200 men on a raid that will kill more than 180 men and boys. He told his men not to kill Mr. Stone, who had treated him well. They did anyway.

Back in the present, on Saturday morning, Katie Armitage led a tour of about 20 history buffs down the streets where it happened, where William Clarke Quantrill bushwhacked his way into Bleeding Kansas history. One of the tour participants, Robert Wilson, of Prairie Village, knows it wasn’t Quantrill’s only raid — one of Wilson’s ancestors was killed in the sack of Olathe. But it’s the Lawrence massacre, now so close to the 149th anniversary, that captures everyone’s imagination.

Quantrill had a hit list of Lawrencians. The prominent politicians and abolitionists he was after included Senator Jim Lane, Reverend Richard Cordley, Governor Charles Robinson and others. None of those targeted were killed, and none of the raiders were brought to justice, save, some would say, Larkin Skaggs, who was shot dead by a Native American resident and thrown into the ravine.

From plaque to plaque, the tour group walks, solemnly nodding their heads as the mental images Armitage paints become clear. But it’s not a morning solely devoted to death.

“The rebuilding was as inspiring as the raid was horrific,” Armitage said as she pointed out the small portions of limestone that stood, then got built around, from a vantage point on New Hampshire.

That street was said to be “littered with bodies” but, as Cordley put it, the town was to start anew “while the bricks were still hot.”

Wilson, himself a history teacher, said he appreciated the story coming alive. Fellow tour-walker Ben McConnell said he grew up hearing bits of information about the raid but was blown away by the suggestion that it just may have been the worst act of domestic terrorism before the Oklahoma City bombing. There’s really just plaques to look at now, but there’s a lot to learn.

But history is complicated, Armitage says. The Jayhawkers had blood on their hands, too. As she points out that there still exists a Quantrill Society commemorating the terrorist — or patriot — in Missouri, one thing history certainly isn’t is dead.

Armitage ends the tour at Framewoods Gallery, 819 Mass., where an old panoramic photo shows rows and rows of well-dressed men and women gathered together in 1913 in front of the Eldridge Hotel. The Eldridge, like the folks in the photo, survived the raid but isn’t here today — it was torn down and rebuilt, this time by choice, in 1927.

You have to use your imagination. But the memories are all around us.