Essex is an unincorporated community located on the east side of Rush Creek in the central part of Jackson Township, Union County, Ohio, United States. It is located at {{#invoke:Coordinates|coord}}{{#coordinates:40|28|57|N|83|18|57|W| |primary |name= }}, at the intersection of State Routes 37 and 739. The Rush Creek Post Office was established in Essex on July 13, 1848. As of 1877, Essex contained two stores, a school-house, and a sawmill. The Post Office changed its name to Rushcreek on November 3, 1894, and was discontinued on June 29, 1907. The mail service is now sent through the Richwood Post Office.