It started when West Indians starting coming to the U.S. in droves in the early 80's and mingling with A.A. who did two things, drug dealing, and being positive on health and spirituality. NYC and Miami were the main places to have dreads. You have to remember the 80's was after a time when drugs hit the community hard, black exploitation films gave black people a negative image to the world, and the whole eating healthy, and being proud of who you were as a black person in the '60's died down in the 70's. So when the dread image came around it helped rebellious blacks with a cause(negative or positive) have something to claim their own and go against the system which made blacks not like anything about themselves.
The wildest drug dealers were Jamaicans, and the people who were on that eating healthy tip were the rastas, and they both had dreads. It was basically a way to rebel against the system, and let people know it, whether positive or negative. People used to be proud to not go along with bullshyt, and let others know what their ways of living was with their looks. They used to call people who get dreads for fashion fake dreads and they got NO RESPECT. Times sure have changed.
[ame="http://www.youtube.com/watch?v=i4sW3jJuVDg"]The Fab 5 - Leflaur Leflah Eshkoshka - YouTube[/ame]
It is bigger now because of Lil' wayne. I grew up in NYC and only certain types of people got dreads then, and it represented something, not just for fashion.