Founded in 1893 by Amos and Persis Gunn, Index was established along the newly completed Great Northern Railway at a time when prospectors and entrepreneurs were pouring into the Cascades in search of opportunity. The town quickly became a gateway to nearby mining districts, including the famous Monte Cristo mines, while also supporting logging, quarrying, and railroad operations.  

By the early 1900s, Index had grown into a bustling mountain community with hotels, businesses, schools, and a thriving downtown. The granite quarry east of town supplied stone used in major projects throughout Washington, including portions of the State Capitol building. As mining declined, Index reinvented itself through recreation, attracting climbers, anglers, hikers, and visitors drawn to the dramatic landscape surrounding the town.  

Today, Index remains one of the most recognizable mountain communities in Washington, where historic buildings, outdoor adventure, and the enduring spirit of the Cascades continue to shape daily life.