Ditto NutBrnHair.
Tri Delta has always had a plan to be national and the have geographical balence of chapters.
That being said, I never heard before that Tri Delt absorbed chapters of another sorority; from what I've heard, we've only affiliated with locals.
eta: I never thought of Tri Delta as a"Southern Sorority" until I visited Atlanta this summer. The number of random people who commented on my Tri Delt tote bag amazed me...not because they knew of Tri Delta, but they said things like you must be an amazing women to belong to such a strong organization and the look of almost admiration because of letters on my sweatshirt/bag on some of their faces. It honestly almost frightened me.
eta: again, cause russ yelled at me for spelling