as structural changes including the addition of another to the tower's height. A clock-like mechanism was installed to rotate the lantern, creating the appearance of a brilliant flash of light every 10 seconds. This system required that the lighthouse keeper crank the weights every three hours through the night to keep the lantern turning. An improved Fresnel lens with prism surfaces created an even more brilliant beacon. An electric light finally replaced the kerosene lantern in 1923, dramatically increasing the intensity of the signal. During World War II, the lighthouse became strategically important for national defense. The last civilian lighthouse keeper resigned, and the United States Coast Guard assumed responsibility for the beacon in 1946. The beacon was automated in 1958. With its original finish tattered by time and harsh weather, the exterior of the lighthouse tower was given a fresh coat of new stucco the same year. The Ohio Department of Natural Resources has maintained the property surrounding the lighthouse since 1972 and accepted ownership of the Marblehead Lighthouse tower in May 1998. The U.S. Coast Guard continues to operate and maintain the lighthouse beacon. In 2012 an LED light was installed. Its green signal flashes every six seconds and is visible for . The distinctive green distinguishes the lighthouse signal from white lights coming from air beacons. Marblehead Lighthouse was one of five lighthouses chosen for the "Lighthouses of the Great Lakes" series postage stamp designed by Howard Koslow in 1995. There was one lighthouse chosen on each of the Great Lakes. The five lighthouses are Split Rock Light on Lake Superior, St Joseph Light on Lake Michigan, Spectacle Reef Light on Lake Huron, Marblehead Light (Ohio) on Lake Erie and Thirty Mile Point Light on Lake Ontario. In 2001-2002 the state renovated the tower and keeper's house at a cost of $500,000. In 2004 the Fresnel lens was returned to the light station from the Marblehead Coast Guard Station, where it was previously on display. Marblehead Lighthouse State Park The lighthouse is now part of the Marblehead Lighthouse State Park. The park features picnic tables and offers views of Lake Erie, Sandusky Bay, Kelleys Island and South Bass Island. The Marblehead Lighthouse Historical Society operates the Marblehead Lighthouse Museum in the old keeper's house. Exhibits include the lighthouse, a Fresnel lens, ice harvesting, ice fishing, local maritime industry, ships, replica Lifesaving Station, local fossils and shipwrecks. Visitors