The West Highland White Terrier Club of America maintains a list of Club affiliated and recognized Westie Rescue organizations nationwide. They also have information about how rescue works. 

www.westieclubamerica.com/rescue/

If you do not live in the Southern California or the Southern Nevada area and wish to either adopt a Westie or rehome a Westie contact the coordinator in your area. All of the Rescue organizations listed below have agreed to abide by the National Rescue Code of Conduct and are recognized by the West Highland White Terrier Club of America.
www.westieclubamerica.com/rescue/coordinators.html

Perhaps you are interested in becoming an active member of a Westie Club, if so, contact the closest club to you.

www.westieclubamerica.com