Montclair is a township in Essex County, New Jersey, United States. As of the 2010 United States Census, the township's population was 37,669, reflecting a decline of 1,308 from the 38,977 counted in the 2000 Census, which had in turn increased by 1,248 from the 37,729 counted in the 1990 Census. As of 2010, it was the 60th-most-populous municipality in New Jersey.Montclair was first formed as a township on April 15, 1868, from portions of Bloomfield Township, so that a second railroad could be built to Montclair. After a referendum held on February 21, 1894, Montclair was reincorporated as a town, effective February 24, 1894. It derives its name from the French mont clair, meaning "clear mountain" or "bright mountain.