Morris Plains is a borough in Morris County, New Jersey, United States. As of the 2010 United States Census, the borough's population was 5,532, reflecting an increase of 296 from the 5,236 counted in the 2000 Census, which had in turn increased by 17 from the 5,219 counted in the 1990 Census.Morris Plains was incorporated as a borough by an act of the New Jersey Legislature on March 15, 1926, from portions of Hanover Township, based on the results of a referendum held on April 15, 1926. The borough's name comes from Lewis Morris, colonial governor of New Jersey.Morris Plains serves as a bedroom community, with many residents traveling to work in New York City. The Morristown Line of NJ Transit provides commuters with direct access to New York Penn Station and to Hoboken Terminal.