Merrimac is located in Essex county Massachusetts with a geographic area of square miles. The total population in Merrimac is 6,926 with 50.4% male and 49.6% female. Children under age 5 represent 5.7% of the population, under age 18 equal 19.1% of the population and over age 65 is 23.8% of the population. The median household income is $79,909, per capita income is $41,596. There are a total of 2,800 housing units with 81.0% owner occupied. Education includes 20.6% of residents that are high school graduates and 44.3% with a bachelor's degree or higher. The average temperature in Merrimac in the summer is 70 degrees, and in the winter 30 degrees.