The Union Pacific and Norfolk Southern corporations announced Tuesday the companies will merge to create America's first transcontinental freight railroad.

Union Pacific is seeking 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.

WASHINGTON (Reuters) -Union Pacific's proposed purchase of smaller rival rail operator Norfolk Southern will need to be approved by the Surface Transportation Board in Washington, an independent federal agency that oversees competition and other areas of importance in the rail industry.