The Website for the Sweet Adelines is http://www.sweetadelineintl.org. Their headquarters is in Tulsa, Oklahoma. I've seem many joint activities sponsored by both the Sweet Adelines and SPEBSQSA. I always assumed they were "sister" organizations, but I don't see anything on either Website that indicates a tie between the organizations. Maybe they developed separately. I think the Sweet Adelines emphasize large-chorus singing over quartets.

Wikipedia says the Sweet Adelines were founded in 1947 in Tulsa, Oklahoma, by wives of SPEBSQSA members who wanted to enjoy the same harmonizing their husbands enjoyed.

By the way, there's a very interesting article about barbershop singing at Wikipedia.

-Joe-