Officials in Montgomery County, Maryland, have spent $2 million to acquire and maintain a two-story colonial home and log cabin formerly believed to be the residence of Josiah Henson, the model for the protagonist in Harriet Beecher Stowe’s novel, “Uncle Tom’s Cabin.” As it turns out, officials had it wrong and Henson never lived in that cabin. We talk with David Rotenstein, who served on the county’s Historic Preservation Commission at the time of the purchase.