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.

Union Pacific acquires Norfolk Southern, forming the first U.S. transcontinental railroad. Read the latest stock analysis on the merger here.

Railroad operator Union Pacific (UNP) is reportedly close to acquiring Norfolk Southern (NSC) for $320 per share in a cash-and-stock deal, which would give its smaller rival a valuation of about $72 billion.