Horseshoe Curve National Historic Landmark, located near Altoona, Pennsylvania, marks an engineering marvel created in February 1854. This is a 220-degree railroad curve built to overcome the height difference at the Alleghenies.Horseshoe Curve was the brainchild of an engineer named J. Even though the curve lengthened the track, it eased the grade to a manageable 1.8% as compared to the 6% - 8% normally required while traveling around mountains.In building this curve, no modern methods were employed. All the work was carried out with help of hand tools, gunpowder, and pack animals.Horseshoe Curve comprises two curves; the northern curve has a radius of 637 feet, while the southern curve has a radius of 609 feet. The west side measures 122 feet higher than the east side.Until 1981, the curve contained 4 tracks. Furthermore, with the arrival of modern train control facilities, the need for the four track system no longer existed.Horseshoe Curve celebrated its centenary in October 1954, with great pomp and ceremony. The Sylvania Electric Company illuminated the curve with more than 6,000 flash bulbs for a photograph.This photograph made it to many newspapers and magazines, including Life magazine. In May 1967, Horseshoe Curve was designated a National Historic Landmark by the National Parks Service.In 1987, special train services were started by the National Park Service rangers to give people a historic ride through the curve.A visitor center, maintained by the Railroaders Memorial Museum, at the foot of the curve, contains exhibits and media presentations depicting the story behind the construction.A funicular from the visitor center takes visitors toward trackside to get a closer look at the historic curve.