Starr Clark and his wife, Harriet, sheltered runaway slaves in the two-story shop as early as 1837 - 24 years before the Civil War began.
In recent decades, the building at 3248-50 Main St. has been a tavern and a boarding house.
The Mexico Historical Society plans to purchase the tin shop from Eileen Yager, who lives next door in Starr Clark's former home, for $25,000, and plans to turn it into a museum, said Jim Hotchkiss, a society director.
He said he thinks the tin shop could become a tourist attraction that would draw people to Mexico.
The Clarks moved to Mexico in 1832. Three years later, Clark sent a petition to Congress asking it to immediately abolish slavery in the nation's capital. In 1838, Clark volunteered to serve on the Mexico Vigilence Committee, which helped freedom seekers.
Underground Railroad researcher Judy Wellman believes Clark was the anonymous author of an 1837 newspaper article that said: "It is my practice whenever a colored man comes into our village to go and invite him to my house and make him free at the same table with my family, let him be bond or free."
Clark was known as an Underground Railroad stationmaster - the person who arranged shelter for any fugitive slaves that came to Mexico, said Barbara Shumway, Mexico's historian.
When Clark died in 1866, the Rev. M. D. Kinney wrote Clark's eulogy: "Starr Clark had but one fundamental article in his political faith, and that was ... impartial justice to all men, without regard to condition or color. For a quarter of a century, during that long and dark period when the colored man had no friends ... and few that dared to be (open) he knew that in Mexico there was at least one man who had for him an open hand, an open purse, and (an) open house."
The Mexico Historical Society has applied for several hundred thousand dollars in grants from the state to help it purchase the tin shop, rip off aluminum siding and otherwise restore the shop to its former condition.
In 2001, the Starr Clark tin shop was placed on the National Register of Historic Places. It is one of 10 sites in New York that the National Parks Service included in its "Network to Freedom" - a program designed to promote and preserve sites that tell the story of the Underground Railroad. It is one of 24 sites designated as part of New York's new Underground Railroad Heritage Trail.