Title: Ohio River
Content:  and the tenth longest and has the eighth largest drainage basin. It serves to separate the Midwestern Great Lakes states from the Upper South states, which were historically border states in the Civil War. The Ohio River is a left (east) and the largest tributary by volume of the Mississippi River in the United States. At the confluence, the Ohio is considerably bigger than the Mississippi, measured by long-term mean discharge. The Ohio River at Cairo is 281,500 cu ft/s (7,960 m3/s); and the Mississippi River at Thebes, Illinois, which is upstream of the confluence, is 208,200 cu ft/s (5,897 m3/s). The Ohio River flow is greater than that of the Mississippi River, so hydrologically the Ohio River is the main stream of the river system.
Title: Ohio River
Content:   The combined Allegheny-Ohio river is 1310 mi long and carries the largest volume of water of any tributary of the Mississippi. The Indians and early European explorers and settlers of the region often considered the Allegheny to be part of the Ohio. The forks (the confluence of the Allegheny and Monongahela rivers at what is now Pittsburgh) were considered a strategic military location by colonial French and British, and later independent American military authorities. The Ohio River is formed by the confluence of the Allegheny and Monongahela rivers at what is now Point State Park in Pittsburgh, Pennsylvania. From there, it flows northwest through Allegheny and Beaver counties, before making an abrupt turn to the south-southwest at the West Virginia–Ohio–Pennsylvania triple-state line (near East Liverpool, Ohio; Chester, 
Title: List of rivers of Ohio
Content:  Ohio is a Midwestern state in the Great Lakes region of the United States. The state takes its name from the Ohio River, whose name in turn originated from the Seneca word  ohiːyo', meaning "good river", "great river" or "large creek". The Ohio River forms its southern border, though nearly all of the river itself belongs to Kentucky and West Virginia. Significant rivers within the state include the Cuyahoga River, Great Miami River, Maumee River, Muskingum River, and Scioto River. The rivers in the northern part of the state drain into the northern Atlantic Ocean via Lake Erie and the St. Lawrence River, and the rivers in the southern part of the state drain into the Gulf of Mexico via the Ohio River and then the Mississippi. The worst weather disaster in Ohio history occurred along the Great Miami River in 1913. Known as the Great Dayton Flood, the entire Miami River watershed flooded, including the downtown business district of Dayton. As a result, the Miami Conservancy District was created as the first major flood plain engineering project in Ohio and the United States.
Title: Ohio River
Content:  Virginia; and Ohioville, Pennsylvania). From there, it forms the border between West Virginia and Ohio, upstream of Wheeling, West Virginia.  The river follows a roughly southwest and then west-northwest course until Cincinnati, before bending to a west-southwest course for most of the remainder of its length. The course forms the northern borders of West Virginia and Kentucky; and the southern borders of Ohio, Indiana and Illinois, until it joins the Mississippi River at the city of Cairo, Illinois. Where the Ohio joins the Mississippi is the lowest elevation in the state of Illinois, at 315 ft. The Mississippi River flows to the Gulf of Mexico on the Atlantic Ocean. Among rivers wholly or mostly in the United States, the Ohio is the second largest by discharge 
Title: Mississippi River
Content:  The Mississippi River is called the Lower Mississippi River from its confluence with the Ohio River to its mouth at the Gulf of Mexico, a distance of about 1000 mi. At the confluence of the Ohio and the Middle Mississippi, the long-term mean discharge of the Ohio at Cairo, Illinois is 281500 cuft/s, while the long-term mean discharge of the Mississippi at Thebes, Illinois (just upriver from Cairo) is 208200 cuft/s. Thus, by volume, the main branch of the Mississippi River system at Cairo can be considered to be the Ohio River (and the Allegheny River further upstream), rather than the Middle Mississippi. In addition to the Ohio River, the major tributaries of the Lower Mississippi River are the White River, flowing in at the 
Title: Ohio River
Content:  The Ohio River is a 981 mi long river in the United States. It is located at the boundary of the Midwestern and Southern United States, flowing southwesterly from far-western Pennsylvania south of Lake Erie to its mouth on the Mississippi River at the southern tip of Illinois. It is the third largest river by discharge volume in the United States and the largest tributary by volume of the north-south flowing Mississippi River that divides the eastern from western United States. The river flows through or along the border of six states, and its drainage basin includes parts of 14 states. Through its largest tributary, the Tennessee River, the basin includes several states of the 
Title: Mississippi River
Content:  The Mississippi River is known as the Middle Mississippi from the Upper Mississippi River's confluence with the Missouri River at St. Louis, Missouri, for 190 mi to its confluence with the Ohio River at Cairo, Illinois. The Middle Mississippi is relatively free-flowing. From St. Louis to the Ohio River confluence, the Middle Mississippi falls 220 ft over 180 mi for an average rate of 1.2 ft/mi. At its confluence with the Ohio River, the Middle Mississippi is 315 ft above sea level. Apart from the Missouri and Meramec rivers of Missouri and the Kaskaskia River of Illinois, no major tributaries enter the Middle Mississippi River.
Title: Great Miami River
Content:  From Dayton it flows southwest past Miamisburg, Franklin, Middletown and Hamilton in the southwest corner of Ohio. In southwestern Hamilton County, it is joined by the Whitewater River approximately 5 mi upstream from its mouth on the Ohio River, just east of the Ohio-Indiana state line, approximately 16 mi west of Cincinnati. The river meanders across the state line near Lawrenceburg, Indiana in the last two miles (3 km) before reaching its mouth approximately ¼ mile east of the border in Ohio. The border of Ohio and Indiana was based on where the confluence of the Ohio and Great Miami Rivers was in 1800.
Title: List of crossings of the Ohio River
Content:  The source of the Ohio River is at the confluence of the Allegheny River and the Monongahela River (40.44194°N, -80.01389°W) at Pittsburgh, Pennsylvania.
Title: Mississippi River System
Content:  The Ohio River runs 981 miles (1582 km) long, starting at the meeting of the Allegheny River and the Monongahela River in Pittsburgh, Pennsylvania; ending in Cairo, Illinois, where it then flows into the Mississippi. The Ohio River drains portions of eight states, including, Illinois, Indiana, New York, Ohio, Kentucky, Pennsylvania, Tennessee, and West Virginia. The river has the capacity to provide enough water for over five million people. At its widest point, it is one mile wide at Smithland dam. The average depth is 24 feet deep which allows multiple species of fish to live there safely. The water is also home to 150 species of fish ranging from catfish to certain species of salmon and trout. The depth also allows for commerce throughout the river on barges. On average the Ohio River transports over 230 million tons of cargo. Typically, the cargo being shipped are energy resources such as coal. These resources account for 70% of the cargo. Along with shipping energy resources, the Ohio River also creates energy with dams and other power-generating facilities. There are 20 dams and 49 other power generating facilities on the Ohio River.

Question: where does the ohio river and the mississippi river meet?
Answer: Cairo, Illinois.