Rensselaer Polytechnic Institute is a private research university in Troy, New York, United States. It is the oldest technological university in the English-speaking world and in the Western Hemisphere. Stephen Van Rensselaer and Amos Eaton established RPI in 1824 for the "application of science to the common purposes of life". Built on a hillside, RPI's 265-acre (107 ha) campus overlooks the city of Troy and the Hudson River. The institute operates an on‑campus business incubator and the 1,250-acre (510 ha) Rensselaer Technology Park. Organizationally, RPI has six main schools which contain 37 departments, with an emphasis on science and technology.