The Panama Canal is a man-made 52-mile-long waterway through Panama that connects the Atlantic and Pacific Oceans. When it opened in 1914, about 1,000 vessels transited the canal. By 2012, more than 815,000 vessels had passed through. In 2016, the waterway was expanded to allow larger vessels with more cargo. Here are five impressive pictures of massive U.S. naval vessels passing through the Panama Canal.