In a five-minute span, Art Ryan morphed from portraying a scared female slave into the overbearing Southern aristocrat who owned her. As his listeners sat on a shaded bench near Independence Hall, he took them back to Philadelphia circa 1855, where they listened to the whispers amongst the staff at a Walnut Street hotel and relived a woman's fear as she stood trembling aboard a steamboat heading to New York.

"I am a slave woman. My master has told me not to speak to colored people. And if any speak to me I am to say I am free. But I am not free. I want to be free," he said in the frightened voice of Jane Johnson, an enslaved African American from North Carolina.

"Now stay put, Jane, and do not talk to anybody!" he roared in the drawl of Col. John Hill Wheeler.

These are Philadelphia's stories of the Underground Railroad, brought to life this summer by the storytellers of Once Upon a Nation.

"I love storytellers, and he's got the voices and he's got the mannerisms," said visitor Rick Nelson, 40, of Stamford, Conn. "And, it's all free."

Once Upon a Nation added Underground Railroad tales to its repertoire of historic stories this year to coincide with the celebration of President Abraham Lincoln's 200th birthday. Besides learning about Harriett Tubman, one of the most famous of abolitionists, listeners will enjoy yarns about Henry "Box" Brown, a Virginia slave who mailed himself to free Pennsylvania in a shipping container in 1849, and 16-year-old Isaac Hopper, who laid the symbolic tracks for the city's section of the railroad.

"Not all of the stories of historic Philadelphia are in the colonial time frame," said Amy Needle, president and CEO of Historic Philadelphia Inc., the nonprofit that oversees the storytelling program. "We decided it was time to celebrate and commemorate the Civil War period."

Because the stories feature lesser-known people - "ordinary men, women and children," Needle said - listeners are often surprised by what they hear.

"You get a lot of, 'Oh, my gosh. I didn't know that' moments," Needle said. "Parents are learning, kids are learning, and it makes for a memorable experience."

The storytellers - most of them from the Philadelphia region - audition over the winter. Those who are chosen undergo three weeks of training, this year by historians from Temple and Pennsylvania State Universities and Independence and Valley Forge National Historical Parks.

Last year, more than 220,000 people visited the 13 Once Upon a Nation benches in Center City, officials estimated. (There are also four benches in Valley Forge.) In Philadelphia, the locations are scattered throughout the historic district, from Washington Square to Franklin Square, Betsy Ross House to Independence Visitor Center.

The benches opened Memorial Day weekend. The stories last from three to five minutes and each storyteller can recount one of five different stories. Some are told in parts to encourage visitors to visit multiple locations. To hear the Underground Railroad stories, listeners should whisper the password - "Freedom" - so the storyteller knows which tale to tell.

The four-part Jane Johnson story began in Signers' Garden at Fifth and Chestnut Streets, with veteran storyteller Ryan. Summoned to the bench by Ryan's bell-ringing, Matthew and Kathryn Loerch found themselves engrossed in the story of Jane Johnson and Col. Wheeler. They followed the tale to three other benches in the area.

Matthew Loerch said the couple came to the city for "history and cheesesteaks," two things their hometown of Houston lacks. They didn't think they'd be hearing about anything past 1800.

"I always think of the Revolution when I think of Philadelphia," said Loerch, 25. "This is unexpected. It's a great surprise."

Dakota and Tristan Dunst of Northern California ran to the storytelling bench in Washington Square and shouted the password at storyteller Dione Shands.

Shands, a first-time storyteller, then relayed the third part of Johnson's story, acting out the roles of a pro-slavery judge and an abolitionist, ending on yet another cliff-hanger.

"Think the story ends there? Oh, no," Shands told the family. For Passmore Williamson, William Still and Jane Johnson are about to explode into a national media sensation.

Shands, an African American with ties to South Carolina, said the Underground Railroad stories are important to her and make her think about her own family's history.

"You never know. They might have been involved in it," she said.

The Dunst parents, Lance, 38, and Katrina, 40, had visited the benches a few years ago and were determined to share the experience with their sons. Katrina Dunst's eyes filled with tears as she described how happy she was to see a program dedicated to preserving these historic tales.

"Every time you come to the benches you learn something," she said. "It was such a great surprise to see how another piece of history fits into their education."

Lance Dunst smiled at his enthusiastic sons.

"They're now engrossed in history," he said. "They're running off to the next place and yelling, 'Freedom!' "