The Straits of Mackinac Shipwreck Preserve are divided in two by a bridge spanning how long?
Mackinac Bridge The Mackinac Bridge ( ) is a suspension bridge spanning the Straits of Mackinac to connect the Upper and Lower Peninsulas of the U.S. state of Michigan. Opened in 1957, the 26372 ft bridge (familiarly known as "Big Mac" and "Mighty Mac") is the world's 19th-longest main span and the longest suspension bridge between anchorages in the Western Hemisphere. The Mackinac Bridge is part of Interstate 75 and the Lakes Michigan and Huron components of the Great Lakes Circle Tours across the straits; it is also a segment of the U.S. North Country National Scenic Trail. The bridge connects the city of St. Ignace on the north end with the village of Mackinaw City on the south.
Monocacy River bridge and viaduct The Monocacy river bridge and viaduct is a 326 ft open deck steel girder bridge with two main spans crossing the river and 2 viaduct sections crossing the floodplain, south of Walkersville, Maryland. Originally constructed by the Frederick and Pennsylvania Line Railroad Company (F&PL). Construction began in late 1871, and continued until July 1872 when the railroad opened that year. It was rebuilt by the Pennsylvania railroad prior first in 1900-1905 as an open deck riveted iron plate under girder bridge. In 1915, the bridge was surveyed as part of the Interstate Commerce Commission's ("ICC") effort to establish freight rates for the Parent railroad. In 1927, the Pennsylvania railroad rebuilt the bridge again using deeper and thicker steel girders, but leaving the masonry piers intact. In 1972, the two 85 foot river spans were washed out by Hurricane Agnes. In 1982, the State of Maryland purchased the bridge as part of the railroad line. In 1995, the State rebuilt the river spans and Pier 3 which is located in the middle of the river crossing was completely reconstructed using concrete to replace the original masonry foundations. In 2015, the State performed minor maintenance on the structure and painted some spans. 