In November 1785 a detachment of U.S. troops under the command of Major John Doughty constructed Fort Harmar, named for Colonel Josiah Harmar, on elevated bottom land on the west side of the Muskingum River at its confluence with the Ohio River.

Construction of the pentagonal fort, which enclosed about three fourths of an acre, was completed in 1786.

The main walls, 120 feet in length, were constructed of large timbers laid horizontally, to a height of 12 or 14 feet.

At each of the five corners were bastions made of logs set upright in the ground. Three of the bastions were mounted with cannon; the two facing the two rivers were not.

Barracks for the enlisted men extended along the main walls, with their roofs sloping inward. They were divided into rooms about 30 feet long and furnished with fireplaces.

Officers’ quarters, made of hewn logs and one and a half or two stories high, were part of the bastions. They had kitchens in the back and stone chimneys.

The barracks on the wall facing the Ohio River were topped with a cupola that served as a sentinel post. A flagstaff was mounted atop the cupola with a room beneath serving as a guardhouse.

A well near the center of the fort supplied water in case of a siege. Water for ordinary purposes was carried from the river.

Gardens and orchards were located west and northwest of the fort.

Between the fort and the Muskingum River stood three large log buildings that served the blacksmith, carpenter, and mechanics.

In 1788 a treaty bower, or cabin, was built outside the northeast bastion of the fort, where the treaty with the Indians was held in 1788-9.