- Your Ad Here Rensselaer County is a county in the U.S. state of New York. As of the 2016 census, the population was 160,070. Its county seat is Troy. Sponsored Links History Rensselaer County was created in 1792. Its name is in honor of the family of Kiliaen van Rensselaer, the original Dutch owner of the land in the area. |