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In fairness, Cobain always gave props to every single band, no matter how uncool or small their following, that influenced him in anyway.

I guess like all genres, no one artist could be credited with creating it. He just brought it into the mainstream. We have him to thank for turning more people onto great bands like Melvins and Meat Puppets, so that can only be a good thing.

Green River Grunge

Most Nirvana fans don't say that. Grunge is a made up label used to market Alternative Rock in the early 90's

Nirvana were the biggest/first band to make that breakthrough.

They may not have started the sound but they did start the Grunge marketing machine.

They were probably the most popular band that brought grunge to the mainstream with "Smells Like Teen Spirit" but they didn't start the sound.

He popularized it and brought it to the mainstream but he sure didn't create it. How could he create a genre that he was influenced by? Two of his influences were Mudhoney and The Melvins, who formed before Nirvana did. Nirvana is a great band but they didn't start it.

grunge is just a label put on a certain kind of rock music so its irrelevant that people say that

They're among the most popular and memorable, so it's natural that people just kind of assume they 'started' it, so to speak.

It doesn't even matter at all you know that right. Grunge is a made-up genre