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The main line of the Pennsylvania Railroad needed a relatively flat route to penetrate the Allegheny Mountains. To achieve this, large earthen bridges or embankments were built across two streambeds at the former Kittanning Point, which allowed the trains to curve 275 feet up the mountainside at the proper grade. Ultimately, the right-of-way of this engineering marvel was expanded to accommodate four tracks. A model of the curve was displayed at the World's Columbian Exposition of 1893 in Chicago, increasing interest in the site to the point that in the first half of the twentieth century, the Horseshoe Curve was considered one of the engineering “Wonders of the World.” In 1940, the railroad gave permission to the city of Altoona to operate