In a wide-ranging lecture on the Underground Railroad, which brought thousands of slaves to freedom in the 19th century, historian Charles Blockson said Wednesday that the role of Philadelphia cannot be overlooked.

"Philadelphia was a major terminal on the Underground Railroad, because of its location as a seaport and so forth," Blockson told about 70 people at Temple University's Sullivan Hall.

Inside the Charles L. Blockson Afro-American Collection, an archive of historical materials he has gathered over 70 of his 80 years, Blockson spoke for more than an hour about the network of safe houses and "conductors" that helped runaway slaves from the South make their way north to freedom.

"No one really knows how the Underground Railroad started," Blockson said. "But Philadelphia had an important part in it."

Blockson, who has written two books on the Underground Railroad, said many African American families in the Philadelphia area, including his own, have ancestors who took part in the network.

He said some of his relatives traveled the Underground Railroad from the South to St. Catharines, Ontario.

Addressing an audience made up of blacks and whites, Blockson said, "Through the Underground Railroad we can connect with our ancestors."

He urged those present to learn about their ancestors. "Don't be upset if you find a black person in your family," Blockson said. "Don't be surprised if you find a white person in your family."

Blockson noted the roles of abolitionists, black and white, with connections to the Philadelphia area, including William Still, Lucretia Mott, Richard Allen, Cyrus Bustill, and Robert Purvis.

"Thomas Garrett was a main operator on the Underground Railroad. He was a great Quaker," Blockson said. "The Underground Railroad had Jews, gentiles, and all kinds of people."

Blockson asked the audience how those on the Underground Railroad could find their way north on cloudy nights, when stars were not visible.

"When the sky was dark and cloudy, they followed the moss on the trees. It grows on the north side," he said.

"An Overview of the Underground Railroad" was part of a project by the Moonstone Arts Center titled "The Underground Railroad in Philadelphia."

The project is a 20-part series of programs throughout October "looking at various aspects of the Underground Railroad in the city," said Larry Robin, director of the arts center. For more details, go to www.moonstoneartscenter.org.

Blockson noted that the abolitionist Harriet Tubman, a leader of the Underground Railroad, was often in Philadelphia and attended church in the city.

He also cited the role of the African Methodist Episcopal Church, which was founded in Philadelphia.

"Wherever I found an A.M.E. church, I found a stop on the Underground Railroad," Blockson said.

The Rev. Mark Kelly Tyler, pastor of Philadelphia's historic Mother Bethel A.M.E. Church, hailed Blockson's lecture.

"It's almost like he has embodied experiences from the past," Tyler said. "It's like those ancestors are speaking through him."

215-854-5717