Pontiac's 1967 GTO is an iconic muscle car. The brand officially went out of business Sunday as General Motors' agreements with dealers expired. Pontiac's sales peaked at nearly one million in 1968, when the brand was prized for its powerful engines and scowling grills.

DETROIT — Pontiac, whose muscle cars drag-raced down boulevards, parked at drive-ins and roared across movie screens, is out of business.

The 84-year-old brand, moribund since General Motors decided to kill it last year as it collapsed into bankruptcy, had been in decline for years. It was undone by a combination of poor corporate strategy and changing driver tastes. On Sunday, GM's agreements with Pontiac dealers expired. Even before GM's bankruptcy, Pontiac's sales had fallen from their peak of nearly one million in 1968, when the brand's speedier models were prized for their powerful engines and scowling grills.

At Pontiac's pinnacle, models like the GTO, Trans Am and Catalina 2+2 were packed with horsepower and sported colors like "Tiger Gold." Burt Reynolds and Sally Field fled the law in a Firebird Trans Am which raced through the 1970s hit movie "Smokey and the Bandit." By the late 1980s, though, Pontiacs were taking off their muscle shirts, putting on suits and trying to act like other cars. The brand had lost its edge.

Bill Hoglund, a retired GM executive who led Pontiac during its "We Build Excitement" ad campaigns, blames the brand's demise on a reorganization under CEO Roger Smith in 1984. That overhaul cut costs by combining Pontiac's manufacturing, engineering and design operations with those of other GM brands."There was no passion for the product," says Hoglund. "The product had to fit what was going on in the corporate system."

Although the moves were necessary to fend off competition from Japanese automakers with lower costs, they yielded Pontiacs that looked and drove like other GM cars. By 2008, the last full year before GM announced Pontiac's shutdown, sales were 267,000, less than a third of those sold in 1968.

Formed in 1926, Pontiac made cars for the working class until a sales slump in the 1950s nearly killed it. GM revived the brand by connecting it to auto racing. From then on, each Pontiac sales boom was driven by speed; each bust generally featured outdated or boring rides. The brand's most storied muscle car, the GTO, came about when some GM engineers took a small car called the Tempest and put a powerful V-8 engine under the hood. The letters stood for "Gran Turismo Omologato," Italian for "ready to race."

Sparked by the GTO, the Pontiac brand thrived, making up 17 percent of the 5.4 million cars and trucks GM sold in the U.S. in 1968.

Pontiac's decline stemmed from a lack of a consistent strategy or leadership. Executives rotated through every few years on their way up the corporate ladder, each with a different vision.

Big economic shifts also damaged the brand. Two gas spikes in the 1970s steered Americans toward smaller cars with more fuel-efficient engines, areas dominated by Japanese automakers in the U.S.

Even after their Pontiac agreements expire, GM dealers will continue to service the cars and honor their warranties.

A low point was the late 1990s, when Pontiac came up with Aztek, an attempt to merge campers with SUVs and win over young, outdoorsy Americans. The vehicle, which seemed more like a cross between a minivan and armored car, flopped.

Despite spells of success during the last 30 years, Pontiac never returned to its supercharged sales of the 1960s.