Isenberg Farm and Woolverton House (“Dorfgrenze,” Hartslog Farm)

This once elaborate summer estate, called “Dorfgrenze” (German for “edge of the village”), was built by William Woolverton, great-grandson of Alexandria's founder, Elizabeth Gemmill. Born in Alexandria, Woolverton began his career as a telegraph agent and operator in 1859 for the PRR, the same job Andrew Carnegie held in his youth. He made a fortune with the PRR and, after 1872, as president of the New York Transfer Company and Bell Telephone. Woolverton and his cousin donated Alexandria's library in 1899 to honor their mothers. The property's name was changed to Hartslog Farm during World War I, when anti-German sentiments ran high. It is now known as the Isenberg farm.

The elaborate barn was built by master builder William S. Varner (1840–c. 1940), of German descent, who trained locally as a carpenter. Rightfully proud of this barn, he signed it with a plaque. Daylight enters the upper level of the large, timber-frame structure through its three windowed cupolas, echoed by those on the adjacent, cement-block milk house. The lower level is illuminated by glass windows at the base of large louvers that ventilate the upper haymow. These windows, designed with hoods on the interior, direct sunlight downward into the basement. Despite its ample size, this structure is now reserved exclusively for heifers. The central operations of the dairy farm take place in two new and much larger, football-field-sized milking parlors at the east end of the farm, where more than four hundred cows are milked three times a day.

The splendid Queen Anne house (Woolverton House) with a deep wraparound one-story porch originally belonged to this farm. It has half timbering above its stone first story, and is dominated by a castellated polygonal corner tower topped by a spire. Similar stonework with a frame upper story characterizes the outbuildings, consisting of a garage and two guest houses.