1920: GM opens the $20 million Durant building in Detroit. Walter P. Chrysler resigns as head of Buick, cashing out his GM stock and forming his own automaker in 1924.

July 27, 1920: Post-war recession slows car sales and drives GM stock prices down to $21, from $27 a week earlier. Durant blames J.P. Morgan's firm for selling off shares and driving down prices, but Durant is again kicked out, this time for good. The Durant building is renamed the General Motors Building.

November 1920: GM sales plunge to 12,700 cars per month, down from 47,000 per month in June. By the end of the year, GM writes off $84 million worth of inventory.

May 10, 1923: Alfred P. Sloan becomes GM president the same year Buick introduces four-wheel brakes and GM Research Corporation introduces Ethyl gasoline.

1924: Sloan rationalizes GM's myriad brands as "a car for every purse and purpose." The step-up price hierarchy is Chevrolet, Oldsmobile, Oakland, Buick and Cadillac. The Milford Proving Grounds opens.

1925: GM acquires the U.K.'s Vauxhall.

1926: Sloan sees too much space in the lineup. The base Olds model costs about 50-percent more than its Chevy counterpart, so Oakland introduces a lower-priced sub-brand to fill the gap: Pontiac, "Chief of the Sixes."

1927: LaSalle's design comes from newly hired Harley Earl's GM Art & Colour Section. The new brand is designed to go after Packard, which is grabbing sales in the price gap between Buick and Cadillac.

1929: GM acquires controlling interest in Adam Opel AG and adds two more sub-brands. First, Oldsmobile launches its upmarket, V-8-powered Viking, to fill the Oakland-to-Buick gap, and late in the year, Buick launches the six-cylinder Marquette, fitting between Pontiac and Olds. Both are produced through late 1930.

January 1930: Cadillac introduces its first V-16-powered car at the New York Auto Show, less than three months after the stock market crash. It's made from two 45-degree V-8s, totaling 452 cubic inches and conservatively rated 165-185 horsepower.

1931: GM forms Holden Limited of Australia.

1934: GM's two-cycle diesel engine powers the first American-produced diesel train.

1935: Opel Olympia is the first mass-produced car with unibody construction while Chevy, Pontiac, Olds, Buick, LaSalle and Cadillac get the all-steel "Turret-top" from Fisher Body.

1936: Buick Century is "the banker's hotrod," with a big Buick's 120-hp, 320.2 cubic-inch inline eight shoehorned into a smaller Special body. It earns its name from the claimed top-speed of 100 mph.

Last week of December 1936: Workers occupy several Flint, Michigan plants (including Fisher Body and Chevy) in a sit-down strike that turns violent, during the height of the Great Depression.

February 11, 1937: The strike ends with GM recognizing the United Auto Workers.

1938: Buick Y-Job, America's first concept is from Harley Earl's Art & Colour Section, now renamed the Styling Department.

1939: GM Futurama exhibit is a highlight of the World's Fair at New York.