Designer Alex Tremulis created the Chrysler Thunderbolt concept car during his time with coachbuilder Briggs Manufacturing Company. The distinctive Thunderbolt featured hidden headlights, a powered retractable hardtop, pushbutton door handles, and pontoon fenders that wrapped completely around the car -- including all four wheels. Five Thunderbolts were built. Chrysler toured them around the country, drawing excited crowds at every stop.

The dramatic Firebird concept car wowed audiences at the 1954 General Motors Motorama. Harley Earl took inspiration from jet fighter planes in designing the vehicle. Power came from a 370-horsepower gas-turbine engine that drove the rear wheels. (The large exhaust nozzle at back was just for show.) When subsequent Firebirds appeared, the original received the retronym "Firebird I."

Ford Motor Company celebrated its 50th anniversary with the X-100, a fully functional concept car billed as a "laboratory on wheels." The X-100 featured more than 50 innovative ideas. Some of them, like the heated seats and the telephone, eventually became commonplace. Others, like the variable-volume horn and the in-car electric shaver, never quite caught on with the public.

The 1951 Le Sabre was the brainchild of Harley Earl, head of design at General Motors from 1928 to 1959. Aviation influences are obvious, from the name itself (taken from U.S. Air Force Sabre jets) to the oval grille that resembles a jet intake. The Le Sabre was a fully functional automobile. Earl himself reportedly put 45,000 miles on its odometer.

Virgil Exner designed the two-seat Chrysler Falcon concept car for the 1955 auto show season. The roadster was close in spirit to the contemporary Chevrolet Corvette and Ford Thunderbird, though the simulated knock-off wheels and external exhaust pipes gave the Falcon a somewhat racier appearance. Chrysler chose not to put the car into production.

The Lincoln Futura, designed by William M. Schmidt, was a sensation at auto shows in 1955. The concept car boasted push-button transmission controls, a 300-horsepower V-8 engine, and a double-dome canopy roof. Hollywood customizer George Barris bought the Futura in 1959 and, a few years later, turned it into the Batmobile for the 1966-1968 Batman television series.

This 1/16-scale model depicts the Packard Predicator, a concept car designed by William Schmidt and Richard Teague. The Packard Predictor concept was a 1956 exercise to visualize a future design direction for Packard. But by 1959, the Packard brand was history.

Cornell Aeronautical Labs did some of the first crash testing of automobiles. In 1957 Cornell teamed with Liberty Mutual Insurance to build this unusual looking concept car that incorporated the lessons learned in testing. The car did not actually run, but it featured ideas like seat belts, head rests, and padded interiors that are incorporated into today's cars.

This 3/8-scale model was built to explore how the future of energy might affect the future of automotive design. The Ford Nucleon would have been powered by a rear-mounted, self-contained nuclear reactor. This atomic-automobile idea assumed, of course, that issues with nuclear safety and the size and weight of nuclear reactors would eventually be resolved. The Nucleon was never produced.

This sharp looking little two-seater created a great "buzz" when racing driver Dan Gurney introduced it at the United States Grand Prix in Watkins Glen, New York, in 1962. Featuring a rear-mounted V-4 engine, it was unlike any Ford ever seen before. The Mustang name later appeared on a sporty four-seater that created its own buzz in 1964.

Looking for a sporty new car, Ford approached the Budd Company in 1961 with the idea of reviving the 1955-1957 Thunderbird. Budd's XT-Bird prototype combined a 1957 Thunderbird body with a 1961 Falcon chassis and powertrain. It captured the original T-Bird's look, but the car's rear seat was too small to be practical. Ford ultimately found its sporty car in the Mustang.

The Budd Company approached American Motors Corporation in 1962 with this concept car, which placed a sporty body and a powerful V-8 on an inexpensive Rambler Ambassador chassis. Fearing it would fail, AMC decided against putting the car into production. Two years later, Ford's Mustang became a massive hit using the same idea of a sporty body on an existing chassis.

Many companies experimented with gas turbine cars after World War II. But only Chrysler actually put them into the public's hands. In 1963, Chrysler lent 50 of these head turners to potential customers to get real-world feedback. Users loved the low maintenance and lack of vibration but complained about sluggish acceleration and poor fuel economy. Rising gasoline prices ultimately killed the turbine dream.

When McKinley Thompson, Jr., joined Ford Motor Company in 1956, he was one of the automotive industry's first African American designers. In 1974 he completed a rugged, easy-to-build vehicle designed for developing countries: the Warrior. Thompson's prototype, built on a Renault 10 chassis, featured a buoyant plastic body and a removable top. Thompson couldn't interest automakers or investors in his bold idea.

Rising gas prices and economic recession meant continued interest in small cars during the early 1980s. Ford designers had cash-strapped students and commuters in mind when they produced this non-drivable 1982 Econocar as a design exercise. Easy to build and repair, the compact car would have been inexpensive to purchase and operate. The Econocar never went into production.

This 1996 concept car exhibits some of the "retro" design ideas popular in the late 1990s. The Lincoln Continental of 1961 inspired its clean, sharp-edged, chrome-outlined profile. The center-opening doors come from the same car. The front end is a re-interpretation of elements from the 1940 Lincoln Continental, while the exhausts exiting from the rear bumpers recall the 1956 Continental Mark II.