GDAX, Gemini, and Kraken all require identification. I'm trying to go through Gemini and Kraken, though, because they have passport as an option instead of a State ID (which I don't have). With Poloniex, I don't think you can go from fiat-to-crypto and their customer service is probably the worse out of all four; in my case, I currently have $200 in SC locked up and am waiting for them to rebroadcast the transaction.
Kraken is also very slow today. Large price drops and volumes on ETH and BTC and all other cryptocurrencies.
Kraken and Gemini inexplicably don't support users from WA state, which is incredibly frustrating.
I live in washington and use itbit.com
gemini just told me they support wa state on my new acct.