Columbus Limestone is a rock formation that stretches in a narrow band from Pickaway County, Ohio, north to Canada’s Pelee Island. Known by this name because of its history of quarrying near Ohio’s capitol city, it formed hundreds of millions of years ago during the Davonian Period, when what is now Ohio lay beneath a sea. Ohioans long valued this workable and attractive stone for construction, and it appears in structures such as the Ohio State House and Marblehead Lighthouse. Limestone processing also produces lime, a substance vital to manufacturing projects from brick mortar to steel. On Kelleys Island, John Clemons opened the first quarry in 1833, and limestone exports became the area’s most lucrative industry by the late 1800s. Formed in 1886, Kelleys Island Lime and Transport Company became the island’s largest quarry operator, and by the 1920s it shipped 1,500,000 tons of stone each year to ports throughout the Great Lakes. Quarrying ended in 1941 after production shifted to Marblehead. During the 1950s, the ODNR bought scattered parcels to combine them into Kelleys Island State Park, which opened in 1956, and the limestone crusher building remains the only remnant of the company’s once-bustling operation.