Brush Prairie, WA has a population of 2,646 and is the 9,481st largest city in the United States. The population density is 344 per sq mi which is 256% higher than the Washington average and 280% higher than the national average. The median age in Brush Prairie is 51 which is approximately 34% higher than the Washington average of 38. In Brush Prairie, 63% of the population over 15 years of age are married, 80% speak English and 1% speak Spanish. 28% of Brush Prairie residents were born in Washington, 60% were born out of state, 1% were born outside of the United States and 11% were foreign born.