page_title: Cairo, Illinois
section_title: Geography
hierarchical_section_title: Cairo, Illinois / Geography
caption_attribution_description: Astronaut photo of the confluence of the Mississippi and Ohio Rivers at Cairo, Illinois. ISS Crew Earth Observations: ISS012-E-15035 Identification Mission ISS012 (Expedition 12) Roll E Frame 15035 Country or Geographic Name USA-ILLINOIS Features CAIRO, MISSISSIPPI R., OHIO R. Center Point Latitude 37.0° N Center Point Longitude -89.2° E Camera Camera Tilt 17° Camera Focal Length 400&#160;mm Camera Kodak DCS760C Electronic Still Camera Film 3060 x 2036 pixel CCD, RGBG array. Quality Percentage of Cloud Cover 0-10% Nadir What is Nadir? Date 2006-01-12 Time 18:38:03 Nadir Point Latitude 37.2° N Nadir Point Longitude -88.3° E Nadir to Photo Center Direction West Sun Azimuth 190° Spacecraft Altitude 185 nautical miles (343&#160;km) Sun Elevation Angle 31° Orbit Number 867 Original image caption The Ohio River becomes a tributary of the Mississippi River directly south of Cairo, Illinois, a small city on the spit of land where the rivers converge (at center of this astronaut photograph). Brown, sediment-laden water flowing generally northeast to south from the Ohio River is distinct from the green and relatively sediment-poor water of the Mississippi River (flowing northwest to south). The color of the rivers in this image is reversed from the usual condition of a green Ohio and a brown Mississippi. This suggests that the very high rainfall in December 2005 over the Appalachians and the northeastern United States has led to greater-than-normal amounts of sediment in the rivers and streams of the Ohio River watershed. The distinct boundary between the two river’s waters indicates that little to no mixing occurs even 5-6 kilometers (3-4 miles) downstream. Cairo became a prosperous port following the Civil War due to increased riverboat and railroad commerce. Small features visible in the image on the Ohio are river barges, which indicate the continued importance of Cairo as a transport hub. Flooding of the Ohio and Mississippi Rivers presents a continual danger to the city; this danger is lessened by the Birds Point-New Madrid Floodway that begins directly to the south of the river confluence. During major flood events, the floodway lessens flood stages upstream (such as at Cairo) and adjacent to the floodway. Part of the extensive levee system associated with flood control of the Mississippi River is visible in the image. Barlow Bottoms (image right), located in adjacent Kentucky, is a wetland bird-watching location that is replenished by periodic floods and releases of Ohio River water.
context_page_description: Cairo is the southernmost city in the U.S. state of Illinois, and is the county seat of Alexander County.
  Cairo is located at the confluence of the Ohio and Mississippi rivers. Fort Defiance, a Civil War camp, was built at the confluence in 1862 by Union General Ulysses S. Grant to control strategic access to the river. Cairo has the lowest elevation of any location in Illinois and is the only Illinois city to be surrounded by levees. It is in the area of Southern Illinois known as Little Egypt.
  Several blocks in the town comprise the Cairo Historic District, listed on the National Register of Historic Places. The Old Customs House is also on the NRHP. The city is part of the Cape Girardeau–Jackson, MO–IL Metropolitan Statistical Area. Being bypassed by transportation changes and industrial restructuring cost many jobs: the population at the 2010 census was 2,831. The city's peak population was 15,203 in 1920.
  The entire city was evacuated during the 2011 Mississippi River Floods, after the Ohio River rose higher than the 1937 flood levels, with the possibility of 15 feet of water inundating Cairo.
context_section_description: Cairo is located at the confluence of the Ohio River with the Mississippi, near Mounds, Illinois. The elevation above sea level is 315 feet (96 m). The lowest point in the state of Illinois is located in Cairo at the Mississippi River.
  According to the 2010 census, Cairo has a total area of 9.086 square miles (23.53 km²), of which 6.97 square miles (18.05 km²) (or 76.71%) is land and 2.116 square miles (5.48 km²) (or 23.29%) is water.
caption: Cairo at the confluence of the Mississippi and Ohio rivers
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