Side fenestration consists of two windows similar to the front windows at ground level, two small windows on the second floor and a fanlight at the gable apex. The roofline has an overhanging eave with a continuation of the denticulation on the pediment. Smooth round pilasters frame the recessed main entrance, topped by a rounded fanlight. It opens into a central hall. There is one room on the east and two on the west. Both are used as exhibit space. There are eight wall vaults, originally used to store records. One has its original metal door. Steel I-beams have been added to support the roof, and braces are visible in the west parlor. The upper stories are used for office and exhibit space, as are the additions. The Holland Land Company was formed late in the 18th century by a group of Dutch investors to dispose of lands they had acquired west of the Genesee River, originally owned by the state of Massachusetts and the Seneca Nation of the Iroquois Confederacy until the 1797 Treaty of Big Tree. The company had acquired them from Robert Morris, who had financed the Continental Army during the Revolutionary War, and needed to sell due to financial troubles in some of his other land dealings. In 1794 they hired Pennsylvania surveyor Joseph Ellicott to survey the five million acres (2 million ha) they had acquired in what is now Western New York and the adjacent areas of Northwestern Pennsylvania. After the survey was finished and the land subdivided into townships, Ellicott was appointed agent in 1800. Working from the present site, Ellicott not only oversaw the sale of individual properties but functioned as the area's sole regional planner, reporting to Paolo Busti, the company's agent in Philadelphia, by mail. He was, a contemporary historian wrote, "the single most powerful person in the area for the first two decades of the century." His decision to sell the land in small parcels rather than large blocks, despite the objections of the company's trustees who wanted the land sold quickly, resulted in settlement by small farmers rather than the establishment of quasi-feudal manors as had occurred in the Hudson Valley. Drawing on his experience laying out the city of Washington, D.C., for Pierre L'Enfant, he surveyed and planned the cities of Buffalo and Batavia. The company's first office was a log cabin; Ellicott cleared the first tree on the site. In 1809 it was replaced with a timber-frame building, in turn replaced by the existing structure in 1815, the third and last one.