Through the first 40 or so years of Denver’s existence, things were quite unsettled when it came to water. A number of water companies formed, delivering water in different ways to different people, competing with each other for business along the way. In 1894, only one company remained standing — the Denver Union Water Company (the precursor to Denver Water).

Citizens were growing tired of increasingly polluted riverside wells and demanded a solution. So, in 1901, the company constructed the first English slow sand filter treatment plant west of the Mississippi: the Kassler treatment plant.

The facility could treat 50 million gallons a day, and low river flows didn’t hinder its operation. Soon Kassler became the cornerstone of Denver’s water system. It was so reliable that it remained in service until 1985, delivering high-quality water to the great-grandchildren of those first settlers.

Check out From water wagons to 50 million gallons a day to learn more about the early days of water in Denver.