There are 27 US Post Offices in Rensselaer County serving a total of 158,467 residents equating to 5,869 residents per post office. It's estimated that approximately 252,931 packages are handled across the 27 county post offices annually. Rensselaer County /r\u025bns\u0259\u02c8l\u026a\u0259r/ is a county in the state of New York, in the United States of America. As of the 2010 census, the population was 159,429. Its county seat is Troy. The county is named in honor of the family of Kiliaen van Rensselaer, the original Dutch owner of the land in the area. Rensselaer County is part of the Albany-Schenectady-Troy, NY Metropolitan Statistical Area."