Ohio. Ohio is a state in the Midwestern region of the United States. It borders Lake Erie to the north, Pennsylvania to the east, West Virginia to the southeast, Kentucky to the southwest, Indiana to the west, and Michigan to the northwest. Of the 50 U.S. states, it is the 34th-largest by area. With a population of nearly 11.8 million, Ohio is the seventh-most populous and tenth-most densely populated state. Its capital and most populous city is Columbus, with other large population centers including Cleveland, Cincinnati, Dayton, Akron, and Toledo. Ohio is nicknamed the Buckeye State after its Ohio buckeye trees, and Ohioans are also known as Buckeyes. Its flag is the only non-rectangular flag of all U.S. states. Ohio derives its name from the Ohio River that forms its southern border, which, in turn, originated from the Seneca word ohiːyo', meaning good river, great river, or large creek. The state was home to several ancient indigenous civilizations, with humans present as early as 10,000 BCE. It arose from the lands west of the Appalachian Mountains that were contested by various native tribes and European colonists from the 17th century through the Northwest Indian Wars of the late 18th century. Ohio was partitioned from the Northwest Territory, the first frontier of the new United States, becoming the 17th state admitted to the Union on March 1, 1803, and the first under the Northwest Ordinance. It was the first post-colonial free state admitted to the union and became one of the earliest and most influential industrial powerhouses during the 20th century. Although it has transitioned to a more information- and service-based economy in the 21st century, it remains an industrial state, ranking seventh in GDP as of 2019, with the third-largest manufacturing sector and second-largest automobile production. Modeled on its federal counterpart, Ohio's government is composed of the executive branch, led by the governor; the legislative branch, consisting of the bicameral Ohio General Assembly; and the judicial branch, led by the state Supreme Court. Ohio occupies 15 seats in the United States House of Representatives, the seventh-largest delegation. Seven presidents of the United States have come from Ohio, earning it the moniker the Mother of Presidents. Archeological evidence of spear points of both the Folsom and Clovis types indicate that the Ohio Valley was inhabited by nomadic people as early as 13,000 BC. These early nomads disappeared from Ohio by 1,000 BC. Between 1,000 and 800 BC, the sedentary Adena culture emerged. The Adena established semi-permanent villages because they domesticated plants, including sunflowers, and grew squash and possibly corn; with hunting and gathering, this cultivation supported more settled, complex villages. The most notable remnant of the Adena culture is the Great Serpent Mound, located in Adams County, Ohio. Around 100 BC, the Adena evolved into the Hopewell people, who were also mound builders. Their complex, large and technologically sophisticated earthworks can be found in modern-day Marietta, Newark, and Circleville. They were also a prolific trading society, their trading network spanning a third of the continent. The Hopewell disappeared from the Ohio Valley about 600 AD. The Mississippian culture rose as the Hopewell culture declined.