Mattawa is an incorporated city in Grant County, Washington, United States. The population was 2,609 at the 2000 census. An estimated population exists between 4500-6500 residents during peak fruit picking/agricultural season(s) and subsides by approximately 2000 residents during non-picking seasons.
The town of Mattawa was originally platted in 1909 by E. and Eva Campbell, but was not incorporated at that time. With the construction of nearby Priest Rapids Dam and Wanapum Dam, the town boomed with construction workers. Mattawa was officially incorporated on June 3, 1958. The Port of Mattawa was also established in 1958. Mattawa is also home to the first straw bale library in the United States. December 3, 2009, the City of Mattawa became a non-charter code city.
Mattawa is located at 46°44′10″N 119°54′7″W / 46.73611°N 119.90194°W / 46.73611; -119.90194 (46.736069, -119.901965).