They may claim to represent 2.7 million nurses, but I'd be surprised if they had more than 2000 members nationwide. They are a joke. The only nurses I know who ever bothered to join their pathetic little group were on faculty somewhere.
Don't bank on it. Some hospitals are closed shops. The last hospital where I worked you paid dues even if you weren't a member. The Dues were taken out of you pay check and donated to the lefty charity of the hospital's choice if you weren't an ANA member. They have a lot of Nurses who are members that totally disagree and refuse to attend meetings or even vote.
Well, I hope you're ready to be really, really surprised then. It's hard to track down a specific membership number, because the ANA, is an umbrella org with 50+ constituant organizations (such as the Texas Nurses Association). However, in dues alone, in 2003, the ANA collected just shy of 13 million dollars. They didn't get that from 2,000 nurses. I asked my wife how many nurses she knows who are members, and her answer was a simple: All of them.