A coachbuilder by trade, Earl pioneered the use of freeform sketching and hand sculpted clay models as automotive design techniques.

By this time, the shop was building custom bodies for Hollywood movie stars, including Roscoe "Fatty" Arbuckle and Tom Mix.

Many luxury-car manufacturers, including GM, did not make bodies at all, opting instead to ship chassis assemblies to a coachbuilder of the buyer's choice.

As head of the newly formed "Art and Colour Section" in 1927, he was initially referred to as one of the "pretty picture boys", and his design studio as being the "Beauty Parlor".

After the early 1930s, Earl seldom drew sketches or did design work himself, usually functioning as an overlord who supervised GM stylists, although he would retain ultimate authority over the styling department until his retirement in 1958.

While many one-off custom automobiles had been made before, the Y-job was the first car built by a mass manufacturer for the sole purpose of determining the public's reaction to new design ideas.

Among Earl's apprentices was English designer David Jones, who worked at its British division at Vauxhall Motors and served in the camouflage section of the Royal Engineers during World War II.

The style caught on throughout Detroit and eventually led to competition between Harley Earl and his counterpart at Chrysler, Virgil Exner, over the size and complexity of tailfins, culminating with those on the 1959 Cadillac models.

Before Earl retired, General Motors became the largest corporation in the world, and design was acknowledged as the leading sales factor within the automotive industry.

[1] He is remembered as the first styling chief in the United States automobile industry, the originator of clay modeling of automotive designs, the wraparound windshield, the hardtop sedan, factory two-tone paint, and tailfins.

One of his concept car designs, the turbine-powered Firebird I, is reproduced in miniature on the Harley J. Earl Trophy, which goes to the winner of the season-opening Daytona 500 NASCAR race.

Actor John Diehl, portraying Earl (or his ghost) was used to symbolize the importance of design in Buick's cars, or as the advertisements put it, the "Spirit of American Style".

[6] In a December 1999 special section in the Detroit Free Press, Earl was ranked the third most significant Michigan artist of the 20th century, behind Aretha Franklin and Stevie Wonder.