Good — Average Score 75/100
State Overview
Water quality across Montana receives an overall grade of B (Good) with an average score of 75 out of 100, based on EPA compliance data from 240 ZIP codes statewide. This is roughly in line with the national average of 75. Approximately 16% of ZIP codes (39 areas) receive a D or F grade, indicating communities with notable water quality concerns that warrant attention. The lowest-scoring area is ZIP code 59035 (Yellowtail) with a score of 29/100. Scores are calculated from EPA Safe Drinking Water Information System (SDWIS) violation records, lead and copper testing results, PFAS monitoring data from UCMR5, and enforcement actions over the past 5 years.
Lowest Scoring ZIP Codes