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Styling seems to have been as much a part of the American automobile as wheels, but in fact it's a relative latecomer to the automotive scene.

The first U.S. styling studio was established by Harley J. Earl in the mid-1920s, and the first concept car -- now an industry staple -- didn't appear until 1939.

Until then, basic vehicle architecture and customer needs practically dictated how a car would look. Early models were built like carriages and had lots of ground clearance to accommodate poor, muddy roads. Engines were packaged directly over the rear axle, for the "horseless carriage" look.

Then engines were moved forward and engine compartments and hoods appeared. Consumers wanted more protection from the weather, and the enclosed body style evolved.

Then in the late '20s, Mr. Earl joined General Motors Corp. and brought the idea of smooth flowing lines -- using full-size clay-model designs for the first time -- to Detroit. The first "styled" U.S. car was the 1927 LaSalle, which borrowed from the sleek, flowing lines of European cars of the era.

Smooth lines then began to take hold in the 1930s -- with varying degrees of success.

But the public didn't want to move too fast. The 1934 DeSoto Airflow featured an extremely innovative aerodynamic shape that was so far ahead of its time it was considered alien and odd looking. It sold poorly.

Automakers learned that public acceptance of styling changes had to be cultivated and manipulated long before new designs hit showrooms, so they started developing "dream cars" that were shown to the public to test out new ideas.

The beautiful one-off Buick Y-Job, built in 1939, was essentially the first concept car.

By 1940, engineers borrowed a page from the Cord and started shifting the passenger compartment ahead of the rear axle, which provided improved ride and handling, and stylists continued to pursue a rounded, massive look. But as fenders and other traditional vehicle details and contours disappeared into a smooth "slab-sided" look at the end of the decade, designers started to look for new ways to decorate these vast areas of squarish sheet metal.

As the 1950s arrived, big became synonymous with better, and automakers competed to get ever longer, lower and wider. The '50s also are described as the "baroque" period of automotive design because stylists piled on tons of purely ornamental details such as chrome trim, tailfins and huge grilles as they tried to develop new styling cues in the absence of fenders and other body contours.

This was the era of planned obsolescence. In 1934, the average length of car ownership was five years, but by 1954, the average had fallen to two years, thanks to annual styling changes that quickly made older models look out of date. The strategy boosted car sales, but by the end of the 1950s stylists had painted themselves into a corner and had nowhere else to go. Buyers were tired of cars pretending to be airplanes and chrome-plated geegaws.

Imports such as the Volkswagen Beetle won increasing favor with consumers because they featured a simple, functional design.

Then consumers and government legislators started to care about fuel economy, safety and pollution. A powerful anti-car and anti-Detroit lobby developed in Washington. All these forces led to a much more restrained and functional look in the 1960s with sharp, square lines that gave the car more of the look of an appliance.

But that doesn't mean nobody had fun in the '60s. Ford Styling Director Eugene Bordinat's design team sketched out a sporty new car that featured new proportions. Its long hood and short deck set the styling world on fire. The Mustang was born.

The two fuel crises of the 1970s caused sudden downsizing moves. Cars grew even more boxy as automakers struggled to retain interior room as they chopped vehicle length.

The soft and rounded aerodynamic look was ushered in during the mid-1980s by the '86 Taurus, which had a profound influence on vehicle styling for a decade. But the Taurus introduced more than just smooth new lines. It introduced a new "team" approach to product development that involves marketing, manufacturing, engineering and purchasing in the design process.

The idea was further refined by Chrysler Corp. in the early '90s with the "platform team" approach it used to develop its revolutionary L-H sedans featuring a "cab-forward" design that pushes the passenger compartment and the wheels out to the vehicle's farthest corners.

Chrysler didn't invent cab-forward, but it used and promoted it more than any other automaker.

Consumers, however, grew bored with soft, aerodynamic lines that tend to make every car look like a jellybean. That's given rise to the latest "edge design" trend that combines flowing aerodynamic lines with sharp creases and edges for a more distinctive look.

As in the past, just when everyone thinks car design can't change much it heads in a dramatically new direction.