The Ohio Company Land Office is the oldest building in the U.S. state

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

 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...

. The Office is listed individually in 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...

 and as a contributing property

Contributing property

In the law regulating historic districts in the United States, a contributing resource or contributing property is any building, structure, or object which adds to the historical integrity or architectural qualities that make the historic district, listed locally or federally, significant...

 to the Marietta Historic District

Marietta Historic District (Marietta, Ohio)

The Marietta Historic District is a historic district in Marietta, Ohio, United States that is listed on the National Register of Historic Places. Among the buildings in the district are ones dating back to 1788, the year in which Marietta was founded as the first white settlement in what is now...

.

The Land Office was built after Ohio Company of Associates

Ohio Company of Associates

The Ohio Company of Associates, also known as the Ohio Company, was a land company which is today credited with becoming the first non-American Indian group to settle in the present-day state of Ohio...

 landed at Marietta

Marietta, Ohio

Marietta is a city in and the county seat of Washington County, Ohio, United States. During 1788, pioneers to the Ohio Country established Marietta as the first permanent American settlement of the new United States in the Northwest Territory. Marietta is located in southeastern Ohio at the mouth...

 in 1788. The Office was built at approximately 39°25′16.75"N 81°27′47.25"W. In 1791 the building was moved away from the Muskingum River

Muskingum River

The Muskingum River is a tributary of the Ohio River, approximately 111 miles long, in southeastern Ohio in the United States. An important commercial route in the 19th century, it flows generally southward through the eastern hill country of Ohio...

 so it could be protected by the guns of Campus Martius

Campus Martius (Ohio)

Campus Martius was a defensive fortification at the Marietta, Ohio settlement, and was home to Rufus Putnam, Benjamin Tupper, Arthur St. Clair, and other pioneers from the Ohio Company of Associates during the Northwest Indian War. Major Anselm Tupper was commander of the Campus Martius during the...

. The building is now part of the Campus Martius Museum

Campus Martius Museum

The Campus Martius Museum interprets Ohio history.Campus Martius was the second fortification in Marietta, Ohio and the first primarily for civilian defense. The Rufus Putnam House, incorporated in the Museum is the only remaining part of the fortification. The museum also includes the Ohio...

complex.