Arlington is a city in northern Snohomish County, Washington, United States, bordered by the city of Marysville to the south. The population was 17,926 at the 2010 census.
Arlington was platted in 1890, and was named after Lord Henry Arlington, a member of Charles II of England's cabinet. Arlington was incorporated as a city in 1903. Since then there have been many important historical figures who have taken residence in Arlington. The city is home to the Stillaguamish Valley Pioneer Museum.
As of the census of 2000, there were 11,713 people, 4,281 households, and 3,095 families residing in the city. The population density was 1,548.4 people per square mile (598.2/km²). There were 4,516 housing units at an average density of 597.0 per square mile (230.6/km²). The racial makeup of the city was 90.01% White, 1.13% African American, 1.04% Native American, 2.20% Asian, 0.32% Pacific Islander, 2.47% from other races, and 2.83% from two or more races. Hispanic or Latino of any race were 5.83% of the population.