The falls of the Big Sioux River were formed 14,000 years ago, at the end of the last ice age, as melting ice eroded a channel down to the bedrock, revealing an abundance of Sioux quartzite. The power and beauty of the falls have attracted people to the area ever since, while Sioux quartzite has been used to construct many of the area's buildings. Incorporated as a city in 1856, Sioux Falls has steadily grown from a population of 17 at the time of...