Before she was J.Lo, she was Jennifer Lopez—rising Bronx-born actress, just Jenny from the block. And though she was best known at the time for having played Selena, she had never so much as stood in a recording studio until it was time to make her own debut album. “It was all so new and scary and exciting,” Lopez tells Apple Music. “That was the seed of who I was—just a girl who used to ride the 6 train and had big dreams and was a hopeless romantic—all of that is right there. I think the best pop album—the best album, period—is when someone just gives you their heart and their soul completely, and they tell you who they are in every way.” In 1999, there was a massive wave of Latin pop stars crossing over with English-language hits—Ricky Martin, Shakira, Enrique Iglesias—and Lopez's debut rode that wave, pushed along by Sony Music chief Tommy Mottola, who had a heavy hand in what would become On the 6. “I was born in the Bronx,” Lopez says, “but I barely spoke Spanish—I still struggle with it to this day. People were accepting Latin artists as just great artists. It was a groundbreaking moment.” She duets in Spanish on “No Me Ames” with future husband Marc Anthony, and the Rodney Jerkins-produced lead single—and her first No. 1 hit—“If You Had My Love” has traces of Latin guitar, but the album's most indelible cross-cultural moment wasn't a hit at all. “It was never a single, but for me, 'Let's Get Loud' is the record that jumped off the album,” Lopez says. “In sports arenas and all around the world now when I perform it, it still brings down the house.” Lopez would go on to star in bigger movies and record bigger hits. But for all the out-of-the-box success and trailblazing, On the 6's most impressive feat may be the way it allowed her to have the nearly frictionless dual-track career that many stars have attempted but few have truly achieved. “I just feel like that's what I always wanted to do and anyone who wasn't on board with that programme got left behind,” Lopez says. “It's just not letting anybody tell you that you can't do something when you know deep down that's part of who you are.”