If you ask people what the first portable MP3 player was, 90 percent will most likely say it's the iPod. Apple's flagship player, released in November of 2001, did change the history of portable audio listening forever. However, Apple didn't invent the portable MP3 player.
Actually, MP3 players have been around since 1998. The first MP3 player that was widely available in the United States was Diamond Multimedia's Rio PMP300 player in 1998. The record industry tried to fight against this, but absolutely failed.
RCA created the very slick RCA LYRA player in 1999. It came with a 32MB CF card, which was considered a lot of memory back in the day. The later RCA LYRA players came with a lot more memory.
Here are five important portable MP3 players that were released before the iPod. They aren't listed in any order of importance; they all contributed to the iPod, whether Apple wants to admit it or not.