Created in 1755 by John Mitchell, the Mitchell Map was widely regarded as the most accurate geographic rendering of North America during the late colonial period. It was heavily relied upon by diplomats during the Treaty of Paris in 1783 to establish the international boundaries of the newly independent United States, and by Congress when passing the Ordinance of 1787 to define future state lines. However, Mitchell had relied on outdated geographic assumptions regarding the Great Lakes region.
His map depicted the southern tip of Lake Michigan significantly farther north than its actual latitude. This cartographic error led Congress to define the boundary between Ohio and the future state of Michigan as a straight line drawn eastward from the southernmost point of Lake Michigan to Lake Erie. When actual surveying occurred years later, the true latitude meant that the line intersected Lake Erie south of the mouth of the Maumee River, placing the booming port city of Toledo inside Michigan Territory.
Ohio claimed the land using an altered border definition known as the Harris Line, while Michigan maintained the original boundary established by the Ordinance line. By 1835, both jurisdictions mobilized armed militias along the Toledo Strip, leading to arrests, minor skirmishes, and a near-fatal stabbing in what became known as the Toledo War. President Andrew Jackson eventually intervened, brokering a compromise: Ohio retained the Toledo Strip, while Michigan was granted statehood and received the mineral-rich Upper Peninsula as compensation, resolving a conflict born entirely from a surveyor's mapmaking mistake.