In Wisconsin, mains water is delivered by local public water systems, regulated by the Wisconsin Dept of Natural Resources (DNR) under the US EPA Safe Drinking Water Act. Typical hardness: Hard to very hard; statewide avg ~172 ppm, most counties hard / very hard. For a specific ZIP, see the EWG Tap Water Database.
Sources: Wisconsin Dept of Natural Resources (DNR), EWG Tap Water Database