Index is a town in Snohomish County, Washington, United States. Prior to settlement by westerners, the Skykomish Indians lived in the area between Sultan and Index. They spoke Lushootseed; fishing the Skykomish River was an important part of their economy. Loggin and lumber booms in the latter half of the 19th century led to the growth of minor settlements in the eastern part of what became Snohomish County in 1861. A gold strike in 1889 at nearby Monte Cristo fueled another influx of prospectors and settlers.The town is named for nearby Mount Index.Being off the main highway, the tiny town of Index is without the commercialism of larger nearby towns. Yet it has already been discovered by rock climbers and day hikers making their way to trailheads for the surrounding cliffs and mountains.