Jim Cramer always reiterates to investors that the transports are the most important group in the market, because if goods are going to be sold, they must first be shipped.
Unfortunately, after a nice rally for the past few years, the Dow Jones Transportation average finally stalled out; it's down 8 percent since November.
Within this group, the railroads have been hit hard, including Union Pacific Corporation which is down more than 13 percent since the beginning of the year. Cramer suspects the blame lies with lower shipments of oil by rail and the coal industry being in rough shape.
When Union Pacific reported in April, it confirmed a 5 percent decline in intermodal shipping. Those are the big boxes that go on container ships, trains and trucks. Anyone in the transport industry knows that when intermodals are down, that's typically bad news for the economy.
"If you have to own a rail, I would pick Union Pacific, but we have to ask ourselves whether the recent down trend will continue, or does this pullback in the railroads represent a buying opportunity as it did once before?" the "Mad Money" host said.
To find out more about where the railroads could be headed and what this means for the U.S., Cramer sat down with Union Pacific CEO Lance Fritz.