Union is located in Mchenry county Illinois with a geographic area of 0.8 square miles. The total population in Union is 680 with 54.3% male and 45.7% female. Children under age 5 represent 2.1% of the population, under age 18 equal 26.3% of the population and over age 65 is 10.1% of the population. The median household income is $95,655, per capita income is $40,315. There are a total of 269 housing units with 79.2% owner occupied. Education includes 24.5% of residents that are high school graduates and 17.1% with a bachelor's degree or higher. The average temperature in Union in the summer is 74 degrees, and in the winter 27 degrees.