Marietta is located in Washington county Ohio with a geographic area of 8.4 square miles. The total population in Marietta is 13,551 with 48.3% male and 51.7% female. Children under age 5 represent 5.2% of the population, under age 18 equal 18.4% of the population and over age 65 is 21.8% of the population. The median household income is $39,439, per capita income is $31,625. There are a total of 5,894 housing units with 55.1% owner occupied. Education includes 31.4% of residents that are high school graduates and 31.8% with a bachelor's degree or higher. The average temperature in Marietta in the summer is 73 degrees, and in the winter 32 degrees.