Union Pacific wants to buy Norfolk Southern in a $85 billion deal that would create the first transcontinental railroad in the U.S, and potentially trigger a final wave of rail mergers across the country. The proposed merger, announced Tuesday, would marry Union Pacific’s vast rail network in the West with Norfolk’s rails that snake across the Eastern United States. The combined railroad would include more than 50,000 miles of track in 43 states with connections to major ports on both coasts. The nation was first linked by rail in 1869, when a golden railroad spike was driven in Utah to...