Cairo is the southernmost city in the U.S. state of Illinois

Illinois

Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...

. It is the county seat

County seat

A county seat is an administrative center, or seat of government, for a county or civil parish. The term is primarily used in the United States....

 of Alexander County

Alexander County, Illinois

Alexander County is a county located in the U.S. state of Illinois. According to the 2010 census, it has a population of 8,238, which is a decrease of 14.1% from 9,590 in 2000. Its county seat is Cairo. Alexander County is part of the Cape Girardeau–Jackson, MO-IL Metropolitan Statistical...

. Cairo is located at the confluence

Confluence

Confluence, in geography, describes the meeting of two or more bodies of water.Confluence may also refer to:* Confluence , a property of term rewriting systems...

 of the Mississippi

Mississippi River

The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...

 and Ohio rivers

Ohio River

The Ohio River is the largest tributary, by volume, of the Mississippi River. At the confluence, the Ohio is even bigger than the Mississippi and, thus, is hydrologically the main stream of the whole river system, including the Allegheny River further upstream...

. The rivers converge at Fort Defiance State Park

Fort Defiance (Illinois)

Fort Defiance, known as Camp Defiance during the American Civil War, is a former military fortification located at the confluence of the Ohio and Mississippi rivers near Cairo in Alexander County, Illinois. The strategic significance of the site has been known since prehistoric times with...

, an American Civil War

American Civil War

The American Civil War was a civil war fought in the United States of America. In response to the election of Abraham Lincoln as President of the United States, 11 southern slave states declared their secession from the United States and formed the Confederate States of America ; the other 25...

 fort that was commanded by General Ulysses S. Grant

Ulysses S. Grant

Ulysses S. Grant was the 18th President of the United States as well as military commander during the Civil War and post-war Reconstruction periods. Under Grant's command, the Union Army defeated the Confederate military and ended the Confederate States of America...

. Cairo has the lowest elevation of any location within Illinois, and is the only city in the state completely surrounded by levees.

Several blocks in the town comprise the Cairo Historic District, listed on the National Register of Historic Places

National Register of Historic Places

The National Register of Historic Places is the United States government's official list of districts, sites, buildings, structures, and objects deemed worthy of preservation...

 (NRHP).