Mellencamp got his start in the mid-1970's as Johnny Cougar (a name chosen by a former manager without Mellencamp's knowledge). His first two albums were not successful, but 1979's John Cougar charted, helped by "I Need a Lover" which hit #28 (and received a further boost when Pat Benatar recorded a cover version on her debut album).
Nothin' Matters and What If It Did solidified Mellencamp's status as an artist in the rise and produced two top 40 hits -- "Ain't Even Done With The Night" (#17) and "This Time" (#27). The album also became the first of nine consecutive LPs to go platinum.
To my ear, the songs off Nothing Matters are more influenced by 1960's pop and have less of an Americana feel than his later work, which may have been intentional. Much ink has been spilled on Mellencamp's desire to be taken seriously as an artist; it seems likely that part of his musical shift may have been designed to show him in a more serious light. However, it is worth pointing out that his early pop songs were extremely well-crafted, with unusually strong lyrics for the genre. (See our Facebook page for an example.)
The video for "Ain't Even Done With The Night" underlines the 1960's pop influences, from the microphone, to the outfits, to the James Brown inspired coat. It also contains one of the best 'man pretending to be a saxophone' scenes in an early 1980's video. The whole thing looks like it was shot on the cheap (perhaps in one take), but I still find it enjoyable.
Of course, Mellencamp's career really took off with 1982's America Fool, which went to #1, helped by the ever present (also #1) "Jack and Diane." (As an interesting side note, those were the only #1's of Mellencamp's career.) And as many readers will know, John Mellencamp remains active in the industry to the present day.