Wyoming runs as six working zones. Cheyenne and the southeastern Wyoming corridor at 200-300 mg/L on Cheyenne Board of Public Utilities Crow Creek and aquifer-supplemented supply. Casper and the central Wyoming corridor at 180-280 mg/L on Casper Water and Casper Mountain-source supply. Laramie and the high-elevation southeastern Wyoming corridor at 160-240 mg/L on Casper Aquifer-source supply. Jackson Hole and the Teton corridor at 140-220 mg/L on Jackson Hole municipal supplies. The Yellowstone-adjacent Cody corridor and northwest Wyoming at 180-260 mg/L on Cody Water and surrounding municipal supplies. The Bakken-adjacent Powder River Basin corridor (Gillette, Sheridan, Buffalo, Wright, Newcastle) at 220-380 mg/L on Gillette-Madison Water and surrounding municipal supplies — among the hardest municipal water in the Mountain West. Rural ranching well-water statewide variable 200-400 mg/L.
HOW IT BREAKS DOWNmoderate to very hard (regional gradient)
Gillette and Powder River Basin coal-corridor commercial is among the hardest municipal water in the Mountain West — same chemistry pattern as the North Dakota Bakken corridor. Jackson Hole and Teton is the most operationally distinctive ultra-luxury second-home commercial book in the Mountain West outside of Aspen. Universal high-elevation UV-accelerated IGU seal degradation pattern statewide — Wyoming state mean elevation 6,700 ft, the highest in the country. Laramie at 7,165 ft. Severe wind exposure year-round — Wyoming runs the heaviest sustained wind exposure of any state in the lower 48. Wildfire-smoke residue June through October in active fire years through western and central Wyoming. Severe winter cold November through March (regularly -30 to -40°F at higher elevations). Cheyenne Frontier Days commercial concentration last full week of July through early August. Powder River Basin coal-and-energy commercial corridor through Gillette (Campbell County is the largest coal-producing county in the country). Casper oil-and-gas commercial concentration. Buffalo Bill heritage commercial through Cody. Wyoming State Capitol (1888) institutional heritage. Union Pacific Railroad heritage commercial through Cheyenne and Laramie.
A blended system means hardness moves with the blend. Two addresses on the same utility can read differently, and the same address can read differently across a year, depending on which source is carrying the load that season.
Wyoming spans 3 hardness bands, which means there is no single answer for the whole state — the method changes as you move across it. Both ends are below.
This is the band where the water starts writing on the glass. Wash with tap — the surfactant holds the minerals in suspension while you work, so the wash pass is not the problem — then rinse with distilled and pull that. The rinse is the whole intervention: it replaces the mineral-bearing water sitting on the glass with water that has nothing in it to leave. This single change resolves most of the "I cleaned it and it still looks bad" complaints in this range, and it does not require buying a system.
A distilled rinse stops being an improvement and becomes the method. Tap water left to dry on glass at this concentration deposits a visible film within minutes, and the film is cumulative: each cleaning that ends in tap water adds a layer that the next cleaning has to get through first. Glass on a sprinkler line or under a runoff drip needs a maintenance interval, not just a better wash — the deposit is arriving faster than a cleaning schedule built around dust would predict.
The hardest water in North America — Phoenix, Las Vegas, West Texas, much of the limestone Midwest. At this concentration calcium carbonate precipitates out of any water that touches the glass and dries, so what you are looking at is essentially limestone, growing one molecular layer at a time. Tap water cannot be part of the final pass under any circumstance, including "just a quick rinse." Above roughly 300 mg/L, buying distilled by the gallon stops making economic sense against a DI filter or a pure-water pole system, and a residential owner cleaning their own glass twice a year is usually better served by a service that already owns one.
Hardest first — the order that matters, because the hard end is where the method has to change. Each figure is a service-area typical for the named utility. Within Wyoming the spread runs from Teton Village at 180 mg/L to Gillette at 300 — a difference big enough that the same bottle of cleaner behaves differently in each.
This page is about Wyoming's water and nothing else. For how cleaning actually works in Wyoming across the year — climate, seasonal timing, the local contaminants, the housing stock — see the Wyoming cleaning guide.
For a figure at your own address rather than your city, the Hard Water Scorer takes a ZIP code. If you run a pure-water system, the TDS diagnostic reads the other end of the same problem.
USGS national hardness survey data and utility Consumer Confidence Reports, 2023 vintage. City figures are service-area typicals for the named utility, not readings from any one tap. State ranges are the lowest and highest typical municipal values across the state, so they bracket the populated area rather than describing an average resident. Where a state blends sources seasonally, the range is wider than any single address will ever see.
Private wells are outside all of it. A well is whatever the rock under it says, and the only number that describes one is a test of that tap. Have a reading that disagrees with this table? Send it to us — a number that contradicts the table is worth more than one that confirms it.