It was 39 years ago today (July 25th, 1980), AC/DC released their biggest selling album ever, Back In Black. It was their first album without lead singer Bon Scott, who had died a few months earlier after passing out and choking on his own vomit following a long night of drinking.

The group quickly decided to press on and hired Brian Johnson from the band Geordie to take over on vocals, and they headed to the Bahamas for about six weeks to do the album. AC/DC had made some serious headway in America before Scott's death, but no one knew how Back In Black would be received. The album took off, and eventually sold over 21 million copies in the U.S.

Brian Johnson admitted that he didn't have a clue how successful Back In Black would turn out to be: "I'd just melted me brain in there, and I didn't know if it was good or bad. That was the first time I'd been in the Bahamas, anyway, or near America, y'know, and you (have to) remember, I was just fascinated by the whole culture and all, and I had no idea what the hell I was doing! And (laughs) lucky, really -- I was a bit lucky, I think."

The album included the singles "You Shook Me All Night Long," which peaked at Number 35 on the Billboard Hot 100, and "Back In Black," which topped out at Number 37.

Despite its massive success, Back In Black never got higher than Number Four on the album charts. The band's next album, For Those About To Rock, reached Number One.

To date, Back In Black, which has sold 22 million copies to date, is at Number Five on the list of the biggest selling albums in the U.S.

AUDIO: BRIAN JOHNSON SAYS HE DIDN'T KNOW HOW GOOD 'BACK IN BLACK' WOULD BE