Nevada
General patterns from public USGS groundwater research, not a prediction for your specific well. Depth, local bedrock, and nearby land use matter more than the state line.
USGS research maps elevated naturally occurring arsenic in private well water across parts of New England, the upper Midwest, and the Southwest, tied to local bedrock and glacial-sediment geology. Arsenic has no taste, smell, or color, so testing is the only way to know.
Some aquifers in the region carry naturally elevated fluoride, worth checking especially for households relying on well water for infant formula.
Parts of the region sit over uranium- and phosphate-bearing bedrock. USGS predictive mapping flags elevated groundwater uranium as more likely here than the national average.