| In 1831, Oceana County was formed from Michilimackinac County. Oceana contained parts of current-day Muskegon, Newaygo, Kent, Mecosta and Montcolm counties. Current-day Oceana was still part of Michilimackinac County at this time. |
In 1840, Oceana was reformed as an unorganized county, attached to Kent. Oceana included part of current-day Muskegon County at this time.
In 1851, Oceana was organized as a county with its 1840 boundaries. However, in 1855, it lost almost a third of its territory, which became a non-county area. This area became the northern portion of Muskegon county in 1859.
