<P> The Philipses used African slaves to build various structures at the Upper Mills and Lower Mills . The Upper Mills saw the building of two gristmills on the Pocantico River as well as a stone manor house, wharf, cooperage, and bake house . Most of the structures were completed by 1697, including the Old Dutch Church of Sleepy Hollow, now a National Historic Landmark . The Lower Mills saw a gristmill and manor house built on the north bank of the Neperhan River . The Philipses' aim was to make the manor a center for agriculture, which the achieved . </P> <P> The slaves came from 22 African cultures from Kongo - Angola . In the 18th century, tenant farmers moved in from Great Britain, the Netherlands, France, Germany, and even elsewhere within North America . By the beginning of the American Revolution in 1776, the population was about 1,000, up from 200 at the time of Frederick I's death . </P> <P> In 1779, Frederick Philipse III, a Loyalist, was attainted for treason along with his family . The manor was confiscated and sold at public auction, and the land was split between 287 buyers . The largest tract of land (about 750 acres (300 ha)), the Upper Mills, was passed to numerous owners until 1951, when it was acquired by Sleepy Hollow Restorations (now Historic Hudson Valley). Thanks to the philanthropy of John D. Rockefeller Jr., about 20 acres (8.1 ha) were restored as an historic site known as Philipsburg Manor . The Lower Mills manor house, Philipse Manor Hall, served as Yonkers City Hall from 1872 until 1908 . Both houses became National Historic Landmarks on November 5, 1961 and are now house museums . </P>

Who owned the philipsburg manor before the break up