Anna is a city in Union County, Illinois, United States. Located in Southern Illinois, the population was 5,136 at the 2000 census. The city is known for being tied to its close neighbor Jonesboro, together known as Anna-Jonesboro. Anna is well renowned for the Anna State Mental Hospital or the Choate Mental Health Care Center. Anna is also a historical sundown town.
Anna is 37°27′40″N 89°14′40″W / 37.46111°N 89.24444°W / 37.46111; -89.24444.
According to the United States Census Bureau, the city has a total area of 3.4 square miles (8.8 km²); of this, 0.01 square miles (0.3%) is water.