We often see clusters of great bands coming from the same city around the same time. London, for example, in the late 70s gave way to some of the greatest bands we’ve ever seen: The Clash, Cock Sparrer, the Sex Pistols, and really too many others to name and do justice. California had two punk rock renaissances, one in the mid 1980s with Black Flag, the Dead Kennedys, and Agent Orange (see ‘american hardcore’ for the details). The other occurred in the mid 1990s with Rancid, Face to Face, and the Swingin’ Utters (see the documentary ‘one nine nine four’ for the story). Lately Gainesville, Florida (the Fest, Against Me!, No Idea Records) and New Jersey (the Gaslight Anthem, the Disconnects) have been getting a lot of attention.
I think that we notice these bands in clusters because for a band to succeed and be heard a local network of venues, promoters, bands, labels, and fans are needed as a support network. You need people to show up, different places to play, and labels to release your records. Trying to make it on your own, without these things would be a an uphill battle.