Numerous large mergers occurred in the United States beginning in the 1960s. In 1968, the Pennsylvania and New York Central railroads combined to form the Penn Central, to which was later added the New York, New Haven, and Hartford railroad. The Penn Central declared bankruptcy in 1970. In 1976, it and other failed railroads in the Northeast including the Erie Lackawanna, Lehigh Valley, and Reading were merged by an act of Congress to form the Consolidated Rail Corporation (Conrail).
A B&O passenger extra powered by a trio of GP9s, West Virginia station on May 12, 1963.
Following WWII and into the 1950s railroads watched helplessly as passenger traffic plummeted and not even new equipment and promotional advertising could sway passengers back to the rails. Some lines continued to spend money on new streamliners, such as the Pennsylvania Railroad, for passengers that never came. The railroad industry after the 1940s also saw a slow decline in freight traffic, particularly less-than-carload (LCL) as the new interstate highway system began to take its toll.
After the end of the war one of the first tasks set forth by many railroads was to retire the iconic steam locomotive as fast as they could. The efficiency of diesel locomotives could not be argued and most lines had completed the switch by the mid-'50s while all Class Is had abandoned steam by 1960. It would take the diesel-electric locomotive nearly fifty years to equal the horsepower output of the steam locomotive during its technological height. However, diesels offered an advantage that far surpassed steamers and it was the deciding factor in them becoming the prime choice of motive power, efficiency.
In 1970, the Great Northern, Northern Pacific, and Burlington merged into Burlington Northern (BN); later, BN absorbed the St. Louis-San Francisco (Frisco) Railroad, becoming the Burlington Northern Santa Fe.
The Chesapeake and Ohio, Baltimore and Ohio, and Western Maryland railroads became affiliated into the Chessie System. In 1981 Chessie merged with the Family Lines a combination of the Seaboard Coast Line, Louisville and Nashville, and Clinchfield to form CSX Corporation. In 1996 the U.S. government approved the merger of the Union Pacific and the Southern Pacific railroads, and in the late 1990s Conrails lines were split between CSX and the Norfolk Southern.