From Ohio History Central
The Toledo War was a border dispute between the State of Ohio and the Michigan Territory during the first several decades of the nineteenth century.
The Northwest Ordinance of 1787 established the northern boundary of Ohio as "an east west line drawn through the southerly bend of extreme of Lake Michigan." The United States Congress restated this line as Ohio's northern boundary in the Enabling Act of 1802, the legislation that led Ohio to become a state. The Congress also used the same language when it established the Michigan Territory in 1805. The Congress incorrectly believed that the line would intersect Lake Erie north of the Maumee River's mouth. During the Ohio Constitutional Convention of 1802, delegates received word from a fur trapper that the line would actually fall south of the Maumee River. The convention delegates stipulated in the Ohio Constitution of 1803 that Ohio's northern boundary must include the Maumee River's mouth. The United States Congress accepted Ohio's constitution, but it never formally acted on the convention's boundary proviso. The failure of Congress to act led to thirty years of conflict between Ohio and the Michigan Territory.