ROCKVILLE, Md. – In the brisk Washington real estate market, the white colonial was an easy sale – three bedrooms, easy access to a major commuting route and an acre of land, a rarity in the tightly packed suburbs.

However, the 18th century house had one thing the McMansions could never claim – the original Uncle Tom’s cabin.

Attached to the side is a small, one-room building, its walls made of graying split oak beams. A massive stone chimney rises at the back, above the large hearth where slaves once tended meals for a plantation owner.

Among the farm’s slaves was Josiah Henson, the man whom Harriet Beecher Stowe used as a model for the Uncle Tom character in her 1852 novel on slavery, “Uncle Tom’s Cabin.”

Less than a month after being put on the market for about $1 million, the cabin and the house are being purchased by Montgomery County.

“We don’t want it to turn into a dentist’s office,” said Peggy Erickson, executive director of Heritage Montgomery, an agency that promotes historic tourism and that worked with the county to raise money to buy the house.