The First Principal Meridian is a meridian that began at the junction of the Ohio River

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...

 and Great Miami River

Great Miami River

The Great Miami River is a tributary of the Ohio River, approximately long, in southwestern Ohio in the United States...

. It extends north on the boundary line between the states of Ohio

Ohio

Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...

 and Indiana

Indiana

Indiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...

, and roughly approximates to the meridian of longitude 84° 48' 50" west from Greenwich. The ranges of the public surveys in the state of Ohio, west of the Scioto River

Scioto River

The Scioto River is a river in central and southern Ohio more than 231 miles in length. It rises in Auglaize County in west central Ohio, flows through Columbus, Ohio, where it collects its largest tributary, the Olentangy River, and meets the Ohio River at Portsmouth...

, are (in part) numbered from this meridian.