Union Pacific Corp. agreed to acquire Norfolk Southern Corp. in a cash-and-stock transaction valued at $85 billion, forming a transcontinental rail behemoth in what stands to be the industry’s largest deal ever.

Union Pacific offers $20 billion cash and one share of its stock to buy Norfolk Southern Tuesday in a merger that could trigger the final wave of railroad mergers across the country.

Union Pacific Corporation (NYSE:UNP) and Norfolk Southern Corporation (NYSE:NSC) announced an agreement to create America’s first transcontinental railroad. The companies said they will seamlessly connect over 50,