Eldean Covered Bridge, north of Troy, Ohio, crosses the Great Miami River on a bypassed section of County Road 33. Built in 1860 as the second bridge at the site, it is one of the nation’s finest and least altered surviving examples of a Long truss, the 1830 design patented by engineer Stephen H. Long. The Long truss was the first truss system designed using engineering principles and introduced prestressed elements to counteract loads. After the loss of New York’s Old Blenheim Bridge, Eldean became the longest surviving example of its type. Its preservation reflects both its engineering importance and its close retention of a nineteenth-century appearance.