Union Pacific and Norfolk Southern are in merger talks to create the largest railroad in North America that would connect the East and West Coasts.

Railroad operator Union Pacific is holding talks to acquire its smaller rival Norfolk Southern in what would be a megamerger in the railroad industry, according to people familiar with the matter.

Union Pacific currently has a market value of about $140 billion, while Norfolk Southern is valued at around $60 billion. Following news of the negotiations, shares of Norfolk Southern rose by 4% in after-hours trading, while Union Pacific’s stock fell roughly 2% before reversing to a slight gain.