The moniker was taken from remarks by a Southern planter who said:: "The Negroes escape into Canada as easily as if they traveled on a railroad which runs beneath the ground."

Runaway slaves were called "freight," routes were "lines," stopping places were "stations" and those who helped the slaves - men and women, black and white - were called "conductors."

Deemed too small just two decades later, it was replaced with a bigger building in 1867 - an early English design incorporating a rust-colored limestone facade and exposed stone buttresses along each side.

The Civil War had ended by the time the second church was built, but the underground passageway and entrance into the basement were retained. While few documents remain - and no construction drawings of the tunnel exist - there is little question the church and its founding members were involved in the underground railway.

The Rev. William Salter, pastor of the church from 1846 to 1910, was well-known for hiding slaves in his home and barn.

He was active in the Abolitionists Society of Iowa. And letters to Salter from a Missouri minister on file at the Iowa State Department of History and Archives unmistakably referred to runaway slaves heading to Burlington:

"Dear Brother Salter, I would inform you in confidence that there is a colored brother in your city who has left his master . . . you will be kind enough to find him out, and do all you can for him . . . Do not trust anyone, not even this brother, that I am the sender of this information, as I am still in that section where he is from . . ."

People who helped runaway slaves did so at great risk. The Federal Fugitive Slave Act of 1793, made even more harsh in 1850, made it a crime to help slaves gain freedom.

Armed Missouri slave owners would sometimes ride into Iowa on horseback with baying bloodhounds chasing their "property."

A band of Missouri slave catchers once set fire to a church in Denmark, a village south of Burlington, when they didn't find any slaves in the area.

"We are very proud of the early legacy toward social justice of our church," said First Congregational Pastor Roy Backus. "In looking back at our church's commitment to the Underground Railroad, it has helped us recognize the continued spiritual and social needs of our community and world."

A December 13, 1840, diary entry by the pastor of the First Congregational Church of Thomaston, Conn., reads: "Took up a collection (today) for the Amistad captives," referring to the imprisoned Africans taken from the slave ship Amistad by the American Navy and put on trial as mutineers and murderers.

This was a little-known piece of American history before Steven Spielberg made the recent movie of the same name.

Harriet Beecher Stowe, author of the 1852 novel "Uncle Tom's Cabin," was also a Congregationalist.

The book, with its vivid descriptions of suffering and oppression, inflamed many Northerners .

Backus is working on a doctoral dissertation for Marquette University concerning the life and teachings of Lyman Beecher, a Congregationalist minister and Stowe's father.

Congregationalism was also a predominate force behind the creation of the American Missionary Association in 1846, a nondenominational reform society that sought the end of slavery.

After the Civil War, the association sent teachers, who were often targets of Ku Klux Klan hostility, into the South to teach recently emancipated African-Americans to read.

Other denominations struggled to eliminate slavery, especially Quakers, Mennonites, Presbyterians and Methodists.

Many church members were "conductors" on the Underground Railroad.

"Congregationalists have always believed that individuals can make important contributions to the benefit of humankind," said Backus.