State Route 109 (SR 109) is a 52.94-mile (85.20 km) state route that runs between Ottawa and the Michigan state line in the US state of Ohio. It crosses a major river, the Maumee, east of Napoleon. Most of the route is a rural two-lane highway and passes through both farmland and residential properties.The highway was first signed in 1930 on much the same alignment as today. SR 109 replaced the SR 65 designation, between SR 110 and the Michigan state line, that dates back to 1923.