Langley, WA. Online Offers. Langley is a town in Island County, Washington, United States near the eastern end of the north shore of the south end of Whidbey Island. It is the third largest incorporated area on Whidbey. The population was 1,035 at the 2010 census, while the ZCTA for Langley's post office had a population of 4,878. The geographical area of the city is only 0.8 square miles (2.1 km²) but the ZCTA includes 26.20 square miles (67.86 km²).