Cairo is a city located in Alexander County Illinois. It is also the county seat of Alexander County. With a 2020 population of 1,878, it is the 495th largest city in Illinois and the 7845th largest city in the United States . Cairo is currently declining at a rate of -5.15% annually and its population has decreased by -33.66% since the most recent census, which recorded a population of 2,831 in 2010. Cairo reached it's highest population of in . Spanning over 9 miles, Cairo has a population density of 269 people per square mile.
The average household income in Cairo is $40,249 with a poverty rate of 34.00%. The median rental costs in recent years comes to $425 per month, and the median house value is $28,200. The median age in Cairo is 37.9 years, 42.2 years for males, and 37 years for females.