The Grand Lake St. Marys Lighthouse, also known as the "Northwoods Lighthouse", is a historic lighthouse on Grand Lake St. Marys, a reservoir in the far western part of the U.S. state of Ohio. Located east of the city of Celina in Mercer County, the lighthouse was built in 1923, using a plan modelled after the Eddystone Lighthouse off the coast of Cornwall in the United Kingdom.[2]