Lower Gallatin River near Manhattan, Montana March 2008 – Mike Cline, Public domain – Wikimedia Commons Manhattan is located in Montana. About 2,086 people live here (as of 2020). Between 2010 and 2020, the population grew from 1,520 to 2,086. The region is at 1294 meters above sea level. The area covers about 4.5 square kilometers. There are about 88 streets in Manhattan. The postal codes are 59741. The dialing code is 406. Manhattan is town in Gallatin County, Montana, United States. Among other things, Manhattan has supermarkets, museums and schools.