Union Pacific Corp. agreed to acquire Norfolk Southern Corp. in a $72 billion cash-and-stock transaction, forming the only US transcontinental railroad in what stands to be the industry’s largest deal ever.

Union Pacific said on July 29 that it had agreed to buy smaller rival Norfolk Southern for $85 billion, including debt, in a deal that would create the first transcontinental U.S. railroad.

The merger would create the United States’ first coast-to-coast rail network and span some 50,000 miles across 43 states.