DJ Mark the 45 King (born Mark James), also known as the 45 King, started DJing in New Jersey in the mid-1980s. The nickname "the 45 King" comes from his ability to make beats using obscure 45 RPM records.

The 45 King first gained fame with his breakbeat track "The 900 Number" in 1987. The song featured a looping tenor sax solo from Marva Whitney's "Unwind Yourself." The 45 King was signed to Tuff City Records that year and given a production deal. "The 900 Number" remains his signature work, having been resampled by many artists. He was also featured on "1989-Hustlers Convention" album on the UK label Music Of Life, considered by many to be hip-hop's first-ever live album.

In the early 1990's, drug addiction took its toll on the 45 King's career, which caused him to lose a production deal that he signed with Warner Bros. Records. Around this time the 45 King released multiple series of breakbeat records (The Lost Breakbeat series, the Breakapalooza series, etc.) and a few tracks for other emceess, but stayed mainly with his breakbeat record franchises.

Using his popularity from the previous release, the 45 King was able to help the other members of his crew, dubbed the Flavor Unit. The 45 King's second break came when Flavor Unit member Queen Latifah was signed to Tommy Boy Records (at the time home of De La Soul and Stetsasonic) and released the album All Hail the Queen (featuring KRS-One, Daddy-O, and Prince Paul). This album is considered by critics to be the 45 King's best production work.

In 1996 Washington, D.C., based Go-go DJ, DJ Kool scored a big hit with the song "Let Me Clear My Throat." It was simply call-and-response vocals over a chopped half of the "900 Number" beat, but it was popular nationwide. DJ Kool didn't just sample the track, he acknowledged the 45 King's as the song's originator, and the 45 King even remixed the track for Kool.

In 1998 the 45 King produced "It's a Hard Knock Life (Ghetto Anthem)" for Jay-Z. The song was a hit that featured a looped chorus from the Broadway Musical Annie. In 2000, he produced the platinum track "Stan" for Eminem, solidifying his reputation as a top-notch beatmaker.

Currently, the 45 King is supposedly working on a solo project, a compilation of emcees over his beats.