when was it established?
In the 1880s
Arlington, Washington
Arlington was established in the 1880s by settlers and the area was platted as two towns, Arlington and Haller City. 
can you tell me something about arlington, washington? Arlington lies on the Stillaguamish River in the western foothills of the Cascade Range. As of the 2010 U.S. census, Arlington has a population of 17,926
wiki:1116613
Arlington, Washington [SEP] Introduction
Arlington is a city in northern Snohomish County, Washington, United States, part of the Seattle metropolitan area. The city lies on the Stillaguamish River in the western foothills of the Cascade Range, adjacent to the city of Marysville. It is approximately north of Everett, the county seat, and north of Seattle, the region's largest city. As of the 2010 U.S. census, Arlington has a population of 17,926. Arlington was established in the 1880s by settlers and the area was platted as two towns, Arlington and Haller City. Haller City was absorbed by the larger Arlington, which was incorporated as a city in 1903.