The Cincinnati Arch is a broad structural uplift

Tectonic uplift

Tectonic uplift is a geological process most often caused by plate tectonics which increases elevation. The opposite of uplift is subsidence, which results in a decrease in elevation. Uplift may be orogenic or isostatic.-Orogenic uplift:...

 between the Illinois Basin

Illinois Basin

The Illinois Basin is a Paleozoic depositional and structural basin in the United States, centered in and underlying most of the state of Illinois, and extending into southwestern Indiana and western Kentucky...

 to the west, the Michigan Basin

Michigan Basin

The Michigan Basin is a geologic basin centered on the Lower Peninsula of the US state of Michigan. The feature is represented by a nearly circular pattern of geologic sedimentary strata in the area with a nearly uniform structural dip toward the center of the peninsula.The basin is centered in...

 to the northwest and the Appalachian Basin and Black Warrior Basin

Black Warrior Basin

The Black Warrior Basin is a geologic sedimentary basin of western Alabama and northern Mississippi in the United States. It is named for the Black Warrior River and is developed for coal and coalbed methane production, as well as for conventional oil and natural gas production...

 to the east and southeast. It existed as a positive topographic area during Late Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 through the Devonian

Devonian

The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...

 Period which stretched from northern Alabama

Alabama

Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...

 northeastward to the southeastern tip of Ontario

Ontario

Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

. The Nashville Dome of Tennessee

Tennessee

Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...

 and the Jessamine Dome or Lexington Dome of central Kentucky

Kentucky

The Commonwealth of Kentucky is a state located in the East Central United States of America. As classified by the United States Census Bureau, Kentucky is a Southern state, more specifically in the East South Central region. Kentucky is one of four U.S. states constituted as a commonwealth...

 make up the central portion of the arch. In the northern part, north of Cincinnati, Ohio

Cincinnati, Ohio

Cincinnati is a city in the U.S. state of Ohio. Cincinnati is the county seat of Hamilton County. Settled in 1788, the city is located to north of the Ohio River at the Ohio-Kentucky border, near Indiana. The population within city limits is 296,943 according to the 2010 census, making it Ohio's...

, the Cincinnati Arch branches to form the Findlay and Kankakee Arches. The Findlay plunges under Ontario and reappears as the Algonquin Arch further north.

Petroleum

Petroleum

Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

 was first discovered in the Cumberland Saddle in Cumberland County, Kentucky

Cumberland County, Kentucky

Cumberland County is a county located in the state of Kentucky in the United States. It was formed in 1799. As of 2000, the population was 7,147. Its county seat is Burkesville, Kentucky...

in 1829 and the Arch has been a major producer since that time.