The Mukilteo Water District was formed in 1920 and is the oldest active district in the State of Washington, providing service to Mukilteo and South Everett areas. The District was authorized to provide sewer service to its South Everett customers in 1975. In November 2007 voters approved the merger of Olympus Terrace Sewer District into Mukilteo Water District. 

In 2008 the name was changed to Mukilteo Water and Wastewater District. Olympus Terrace Sewer District had been created in 1969 to provide sewer service to the subdivision of Olympus Terrace and expanded over time to eventually provide sewer service to the greater Mukilteo area. The combined District is committed to provide safe, quality service and excellent customer service in a reliable, cost effective manner.