@Jock Scott: What do folks in Scotland do when they do not have a surname that lines up with a clan name? I understand Mr. MacOnion (or Mr. Onion for that matter) wearing a MacOnion tartan. I'm more interested in which clan Mr. Potato (where no Clan MacPotato exists) associates, if any. Or do they simply not associate with a clan? Also, what (based on your experience, as I know you cannot speak for the whole of Scotland) is the participation of Scots in clan associations? Or is simply being a MacOnion enough? I suspect that most clan associations are fueled by people outwith Scotland with Scottish roots or ex-pats, but I'd hate to jump to conclusions there.

As to which tartan, that was easy for me. I think all of my family lines save one or two have been documented as being here in the American colonies prior to the Revolution, and most of them in the Carolinas. Those last few are not documented and so far there are no lines that are documented as being somewhere other than the colonies at any point after the Revolution. I honor all of my Scottish ancestors collectively by wearing the Carolina tartan, the district to which they emigrated.

Right now I'm interested in clan affiliations as it regards to participation in a society, not the wearing of tartans. I don't have the financial wherewithal to join the society for every Scottish ancestor and I'm trying to pare down my options.

Thanks again everyone for your input.

(Still waiting to hear from Kyle Smith and David Pope.)