Anna is a city in Union County, Illinois, United States. Located in Southern Illinois, the population was 4,442 at the 2010 United States Census, a decline from 5,135 in 2000. The city is known for being tied to its close neighbor Jonesboro, together known as Anna-Jonesboro. Anna is renowned for the Anna State Mental Hospital or the Choate Mental Health Care Center. It is also known for its racist acrostic, "Ain't No N*****s Allowed".