Essex, MO has a population of 551 and is the 18,973rd largest city in the United States. The population density is 1,906 per sq mi which is 2106% higher than the Missouri average and 2004% higher than the national average. The median age in Essex is 38 which is approximately 1% lower than the Missouri average of 38. In Essex, 54% of the population over 15 years of age are married, 99% speak English and 1% speak Spanish. 79% of Essex residents were born in Missouri, 21% were born out of state, 0% were born outside of the United States and 0% were foreign born.