 The city of Arlington had a population of 17,926 people at the time of the 2010 U.S. census, making it the ninth largest of eighteen cities in Snohomish County.From 1980 to 2010, Arlington's population increased by over 450 percent, fueled by the construction of suburban housing and annexations of outlying areas.The United States Census Bureau estimates the city's 2019 population at 20,523.