This became a common means of transportation following the Civil War as the railroads began pushing westward, especially among migrant workers who became known as hobos. It continued to be widely used by the destitute and those unable to afford other transportation, especially during times of widespread economic dislocation such as the Great Depression in the United States. Many railroads took a dim view of people hopping freights, and employed security guards known as "bulls" in an attempt to prevent the practice, but some other railroads quietly tolerated the practice. In part this is because many hobos had worked building the railroads, and others were itinerant farm workers who helped provide the cargo which the railroads would then haul back east; a policy of suppressing freighthopping would not have been good business for those railroads.
Some common methods of hitching a ride on a freight train included "riding the rods" (riding underneath a freight car on the car's structural rods), "riding the deck" (riding on top of a railroad car), and riding inside an open boxcar, a gondola car, or an unoccupied caboose. Riding the rods or riding the deck were very dangerous, while riding inside a railroad car was the preferred method if possible. Eventually, railroads began using freight cars without structural rods underneath, to end the practice of riding the rods.
In recent decades, the traditional role of hobos as itinerant workers has fallen off, largely because of increasing prosperity; even most itinerant workers nowadays have cars and drive between jobs, or use bus or airline transportation, and live in motels or temporary housing. Many itinerant and seasonal jobs nowadays pay relatively high wages or even union wages. This is still not, however, the case with seasonal jobs in the agricultural sector. Increasingly, as seasonal agricultural work became the province of immigrants, and other seasonal work became increasingly lucrative, freighthopping became mainly used by the homeless population, or by thrill-seekers in search of a joyride.
Today, although still used by a diminishing number of the homeless population as transportation, and by the few people left who could still properly be called hobos, the practice has undergone something of a revival among thrill-seekers, and among some kids who have adopted the lifestyle as an expression of rebellion against society. With the recent railroad mergers eliminating those railroads who used to tolerate the practice, most railroads today follow a much stricter policy regarding freighthopping than they did a couple of decades ago. The elimination of the caboose and the shift away from boxcars toward intermodal shipping containers has also made the practice more of a challenge.
Books about freighthopping: