Northwest Multiple Listing Service (NWMLS), owned by its member real estate firms, is the largest full-service MLS in the Nor ... thwest. Its membership includes more than 32,000 real estate brokers. The organization, based in Kirkland, Wash., currently serves 26 counties in Washington state. Phone: (425) 820-9200 or toll free (800) 541-0455 Fax: (425) 821-3705; (888) 821-3705 Phone Support Hours: 8am-6pm (Weekdays) 9am-4pm (Weekends) read more