Essex is a city in Stoddard County, Missouri, United States. The population was 472 at the 2010 census. Essex was platted in 1873 a…Essex is a city in Stoddard County, Missouri, United States. The population was 472 at the 2010 census. Essex was platted in 1873 as a stop along the Missouri Pacific Railroad, and named after one Mr. Essex, a railroad official. A post office in Essex has been in operation since 1874.