What are the three largest women's organizations in the U.S.?

I just learned about the "Red Hat Society" They have 65,000 members,
for example. There must be organizations for women that are larger. I
wonder what they are.

Hello bjfogg,

There seem to be some contradictory claims being put forward.  Here
are the organizations I have identified, with claims as made by or for
them cited directly from the relevant web sites.

“The National Organization for Women (NOW) is the largest organization
of feminist activists in the United States. NOW has 500,000
contributing members and 550 chapters in all 50 states and the
District of Columbia.”
http://www.now.org/organization/info.html

Concerned Women for America: There is a claim that CWA is larger than
NOW: “Beverly LaHaye and a handful of women founded Concerned Women
for America. Soon they became the largest women's organization in the
country, more than double the size of NOW in actual dues-paying
members.”
http://www.newsmax.com/commentarchive.shtml?a=2001/6/19/170503 
This site claims CWA  has over 500,000 members
http://www.lafalce.com/about/company/
However, the CWA web site seems to be coy about stating membership
figures. I could only find a figure of 17,784 subscribers to their
mailing list. Also, their membership structure seems to be rather
loose: “Giving a donation of any dollar amount makes you a member of
CWA. We welcome all like-minded women and men.”
http://www.cwfa.org/about.asp

Hadassah: “the largest women's and the largest Zionist membership
organization in the United States, with more than 300,000 members.”
http://www.hadassah.org/pageframe.asp?section=about&page=membership/allaboutmem.html&header=membership&size=50

Chi Omega Sorority: “With over 240,000 initiated members and 170
collegiate chapters, Chi Omega is the largest sorority and second
largest women's organization in the United States”
http://www.chiomega.com/chapters/content/fun.asp?chapterID=17 

Daughters of the American Revolution has over 170,000 members
http://www.dar.org/natsociety/default.html

“The American Business Women's Association (ABWA), founded by Hilary
A. Bufton in Kansas City, Missouri, has been helping working women
meet their personal and professional goals for over 50 years.  At over
70,000 members, ABWA is the fourth largest women's organization in the
U.S.”
http://www.abwaprestige.homestead.com/

Search strategy: “largest women’s organization” “second largest
women’s organization” “third largest women’s organization”

I hope this has answered your question, but please request further
clarification if required.

Thanks. More than I expected!
I wish I could pay more for this answer, but I can't right now. I hope
the 5 star rating helps.

It partly depends on how you define "organization."  The Relief
Society of the Church of Jesus Christ of Latter-day Saints has about 4
million members, about half of them in the United States, and claims
to be the largest women's organization in the world.  It is, of
course, not an independent organization (although it started out that
way).
http://deseretnews.com/dn/view/0,1249,410015769,00.html

Thank you very much for the kind rating, and no worries about the
other matter. An asker has the freedom to set whatever price is
appropriate, and each researcher has the freedom to choose whether or
not to attempt an answer.

And yes, most researchers do very much want to get those 5 stars as
often as possible :)