Rock Island was officially incorporated on December 8, 1930. The site had been previously settled in the late 19th Century and was known as Hammond. The site was thought to be the area where the large city of the area would develop as it was located near the Rock Island Rapids and near the bridge which spanned the Columbia River for the Great Northern Railway. Despite the strategic advantages therein, the large city of the area would become Wenatchee, just seven miles upriver from the site of present-day Rock Island. The nearby Rock Island Rapids would become the site of the first hydroelectric dam on the Columbia River and spur growth in the tiny hamlet. During World War II a silicon smelter would be built in the town of Rock Island closing in 1999.