Eighty-eight years ago, the company's founder, William S. Paley, bought the nascent Columbia Broadcasting System, and those radio stations became the nucleus of a budding broadcast empire.

But on Tuesday, CBS Chairman and Chief Executive Leslie Moonves said the company was exploring strategic options, including a sale or spinoff, of its entire radio division.

"The aim here is to unlock value for our shareholders," said Moonves, who made the announcement during an investor day in New York.

The decision marks the end of an era and highlights the waning influence of commercial radio, which is no longer considered a growth industry. Young adults spend more time listening to digital music files, podcasts and subscription Internet radio services such as Spotify and Pandora. The shift has prompted major advertisers, including car dealerships,on to the division for several months, in part because this year is expected to set records for political ad spending. Radio stations are expected to rake in millions of dollars for campaign commercials.

Although CBS no longer separately breaks out its radio results, its most recent earnings report revealed that radio revenue had fallen 5 percent compared with the year-earlier period.

The proposed sale comes two years after CBS spun off its billboard unit. The company slowly has been jettisoning radio stations. CBS recently sold KFWB-AM (980) in Los Angeles to comply with Federal Communications Commission rules.

Nonetheless, CBS' announcement rocked the radio industry because the radio outlets formed the bedrock of CBS.

In 1927, when talent agent Arthur Judson, who also ran the Columbia Phonograph and Records Co., failed to