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As transistor radios and their price tags got smaller, music stations on AM radio grew in popularity. Corbis photo

As hard as it might be to believe, it was not so long ago when AM music radio ruled.

The coolest kids listened to the hottest hits on AM via portable radios while dads listened intently to ballgames with transistor radios pressed against their ears.

“The Good Guys” on 570 WMCA-AM; “Famous 56, WFIL!” “Seventy-seven, WABC!” “Murray the K and the Swingin’ Soiree” “The Wonderful World of Wibbage!”

Back in the day of the transistor, North Jersey kids might have tuned to Cousin Brucie Morrow, Harry Harrison, Ron Lundy and Dan Ingram broadcasting from New York City, while south Jersey teens listened to Philly rock jocks George Michael, Hy Lit, Jerry Blavat and Long John Wade.

John Bardeen, foreground, Walter Brattain, standing, left, and William Shockley received the 1956 Nobel Prize in Physics for their work on the transistor. Courtesy of Bell Labs

The transistor, which took the radio out of bulky cabinets and put it in the palm of listeners' hands, was developed by John Bardeen, Walter Brattain and William Shockley in 1947. Bardeen, Brattain and Shockley were engineers at Bell Laboratories in Murray Hill when they came up with the tiny transistor, which eliminated the need for large vacuum tubes and instantly made radios portable.

By 1948, the three engineers had developed a prototype transistor radio. The Regency TR-1, built by Texas Instruments in 1954, was the first practical transistor radio made available to the public and sold for $49.95 – equivalent to more than $400 in the 21st century. By the 1960s, the cost of a similar but more powerful radio had dropped below $10.

Thank you, AM radio, for bringing us top-40 hits, the British Invasion, prize patrols and wisecracking DJs. And thank you Bardeen, Brattain and Shockley, whose innovation helped make music mobile.

What was your favorite radio station growing up? Let the ranking begin!