Examples of IRC § 501(c)(6) organizations include the Chamber of Commerce, Jaycees, American Bar Association, American Medical Association, and National Association of Manufacturers.
The AMA is a c6 because: lobbying
The organizational definitions in IRC §§ 501(c)(4), (c)(5), and (c)(6) do not contain any explicit limitations on lobbying. The organizations described in these three sections may participate in an unrestricted amount of lobbying so long as the lobbying is related to the organization's exempt purpose. In fact, organizations whose sole activity is lobbying may be recognized under these sections...{etc}
Citation> Tax-Exempt Organizations: Political Activity
Restrictions and Disclosure Requirements, Order Code RL33377
There are several larger; the US Chamber of Commerce is #1 -- AMA is big, but not even the biggest healthcare lobbying entity (BC/BS and the American Hospital Association are bigger than AMA) [1].
