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

The Surface Transportation Board said on Wednesday that Union Pacific and Norfolk Southern have formally filed a notice of intent to combine, triggering the U.S. regulatory review process for a proposed $85 billion merger between the two major railroads.

A proposed merger between Norfolk Southern and Union Pacific was announced Tuesday, causing a lot of uncertainty for Central Pennsylvania. If the $85 billion merger goes through, Union Pacific will acquire Norfolk Southern,