6 seasons
1 - The Crowder family season
http://en.wikipedia.org/wiki/Justified_%28season_1%29
2 - The Bennett family season
http://en.wikipedia.org/wiki/Justified_%28season_2%29
3 - The Robert Quarles season
http://en.wikipedia.org/wiki/Justified_%28season_3%29
4 - The Mystery season, where Sheriff Shelby turns out to be some 30 year missing guy and they nab mafia boss Theo Tonin in a warehouse
http://en.wikipedia.org/wiki/Justified_%28season_4%29
5 - The Crowe cousins season
http://en.wikipedia.org/wiki/Justified_%28season_5%29
6 - The Boyd/Markham/final season
http://en.wikipedia.org/wiki/Justified_%28season_6%29