Dahl became a millionaire over a matter of months after inventing the Pet Rock in 1975
Credit: Corbis

Gary Dahl, the man who became a millionaire by selling ordinary rocks, died on March 23 at the age of 78.

Dahl, an advertising copywriter, thought up the Pet Rock in 1975, after listening to friends complain about having to care for actual pets. The Pet Rock became an unlikely fad through Christmas that year. They sold for $4 each, and Dahl became a millionaire by the time the product was discontinued in February 1976.

In a 1975 PEOPLE interview, Dahl tried to explain the product’s odd success. “People are so damn bored, tired of all their problems. This takes them on a fantasy trip – you might say we’ve packaged a sense of humor.”

The article describes the Pet Rock in grand terms: “They are not, of course, prosaic pebbles, but egg-shaped Mexican beach stones, nestled on a bed of excelsior and packaged in a little doggy carrying case, equipped with breathing holes.”

According to the New York Times obituary, Dahl’s post-Pet Rock career saw him running a saloon and sail boat brokerage. He wrote Advertising for Dummies in 2001.

Dahl died in Jacksonville, Oregon.