There were two major land purchases made by Van K(C)eulens in New Netherlandt(New York)in the mid 1600s, both being on the Pappermemmins Eiland(Manhats Island, Manhattan).
In 1639, Conraet van Keulen secured a Patens for 100 Morgens at Otterspoor, renamed Van Keulens Hook. This being located between present day 108th and 125th Streets, along the River, in Harlem. He was also named as a Lessor on a parcel called Bestevears Kreupelbosch(Leather Swamp) in a document dated 14 December, 1640.
Mathijs Jansen van Ceulen received a land Patens for 50 Morgens of land at the North East tip of Manhattan Island in August, 1646, which was named Van Keulens Bouwerie. Today that land is occupied by Columbia University, Bakers field, and lands to the East of route 9. Route 9 is approxiamitely where the ferry to the mainland was located in the 1600s.