On May 1, 1971, there were 26 railroads in the United States that were eligible to participate in the formation of Amtrak. Twenty chose to join Amtrak in 1971, and one more eventually joined in 1979. Of the remaining five, four ultimately discontinued their services, while one was taken over by a state agency.

Twenty railroads opted to participate. Each contributed rolling stock, equipment, and financial capital to the new government-sponsored entity. In return, the railroads received the right to discontinue intercity passenger rail services; most received tax breaks, while some received common stock in Amtrak. The four railroads that accepted stock were the Burlington Northern Railroad, the Grand Trunk Western Railroad, the Chicago, Milwaukee, St. Paul and Pacific Railroad ("Milwaukee Road"), and Penn Central.^[1] Because Amtrak discontinued many passenger rail routes when it commenced operations, some of the participating railroads did not host successor passenger rail service. The twenty participating railroads were:^[2]

There were six railroads eligible to participate in the formation of Amtrak that declined to spin off their passenger rail services. The intercity passenger operations of those six railroads eventually were absorbed by Amtrak or another governmental entity, or discontinued. The six non-participating railroads and disposition of their routes were as follows:

A few major railroads with operations in the United States were not eligible to participate in the formation of Amtrak: