(Reuters) -Union Pacific said on Tuesday it would buy smaller rival Norfolk Southern in an $85-billion deal to create the country's first coast-to-coast freight rail operator.

Such mergers have historically reshaped the rail map, consolidating regional carriers into some dominant networks, but often come under intense scrutiny from the Surface Transportation Board.

Landmark mergers in the past - such as the creation of BNSF and between Union Pacific and Southern Pacific - have set the stage for today's concentrated rail network, often triggering both operational gains and regulatory pushback.

Here are some of the largest railroad deals in the past three decades:

Year Merger Deal value Note

1995 Burlington Northern & $4.1 Created one of the

Santa Fe billion largest U.S.

railroads at the

time

1996 Union Pacific & $5.4 The merger caused

Southern Pacific billion significant

operational

problems and

shipping delays

that led to tougher

regulatory

standards

1998 CSX & Norfolk Southern $10.2 Conrail was split

split Conrail billion between CSX and

Norfolk Southern in

a joint acquisition

2023 Canadian Pacific & $31 billion First single-line

Kansas City Southern railroad linking

the U.S., Canada

and Mexico

2025 Union Pacific & First

Norfolk Southern $85 billion coast-to-coast

freight rail

operator