Roller coasters are thrill rides that operate like a railroad track and are a highlight of theme parks around the world. They are made from steel or wood and comprise a series of hills and drops, sudden turns, track loops and corkscrew-like elements. The roller coaster is a favorite ride of thrill seekers, and has evolved considerably from its days as a glorified slide.

Experts argue about the first roller coaster ride. Some suggest that purposely build ice slides in 17th century Russia qualify. Others claim an 1812 French construct that featured cars locked onto a track is the first true version of the ride. In 1881, designer LaMarcus Adna Thompson envisioned what would become America’s first coaster, the Switchback Railway. The Coney Island roller coaster featured bench-like seating and consisted of coasting down a 600 ft (182 m) track to a second station, where the car would be switched to a return track. The track was replaced with a complete oval circuit a few years later.

A major innovation to the roller coaster was the lift hill, created by Phillip Hinkle in 1885 and first used on his ride, Gravity Pleasure Road. The lift hill was placed at the beginning of the ride, using a cable or chain to haul the ride cars up a steep slope. The lift hill remains common in modern roller coasters, although the original hills were about 40 ft (12 m) high, while today they reach soaring heights of up to 456 ft (139 m.)

In 1959, Disneyland opened the first steel-track roller coaster, the Matterhorn Bobsleds. Until that point, most coasters were wooden structures. Steel tracks, unlike their wooden predecessors, are highly flexible in design, since the steel components can be manufactured in any shape desired. This new technology allowed the incorporation of the thrill elements enjoyed today such as loops and corkscrews.

Early roller coasters and some modern ones were propelled by a chain or cable lift to the top of a hill, and then allowed to coast through their circuit. Modern innovation has created several alternative ways to power a coaster. Since the late 20th century, launched roller coasters have become popular, using electromagnetic, hydraulic or pneumatic systems to propel the ride through its course. These systems are believed by many to provide a smoother ride than early chain/cable versions. Some new coasters feature an elevator lift, which launches vertically to place the train at the top of the lift hill, eliminating the long, uphill climb.

Roller coaster records are sought after by manufacturers and parks alike, to give distinction to their rides. As of 2008, the records for tallest, highest drop and fastest steel coaster all belong to one ride, Kingda Ka at Six Flags Great Adventure in New Jersey. The record for tallest vertical loop goes to Superman: Krypton Coaster at Six Flags Fiesta Texas, at an impressive 145 ft (44m.) For those who truly cannot get enough of thrill ride fun, the park featuring the most coasters is Cedar Point in Ohio, with 17 individual roller coaster rides.

Despite their reputation as thrill rides, modern roller coasters are extremely safe and controlled systems. A 2001 study by the US Consumer Product Safety Commission estimated that out of 319 million visitors per year to US amusement parks, 134 people received injuries needing hospitalization and two fatalities occurred. Modern coasters employ multiple safeguards, however, accidents can occur.

Most often, these are the result of ride-operator carelessness in following safety procedures, but can also be caused by mechanical failure. Other accidents can be caused by riders with previous injuries or those with medical conditions unsuited to extreme thrill rides. Before boarding any extreme ride, review the safety information and check with your doctor if you have any health concerns.