Locations
| Name | Sites | Samples |
|---|---|---|
| Pratt County | 2 | 2 |
| Prentiss County | 2 | 5 |
| Presidio County | 29 | 160 |
| Prince George County | 5 | 68 |
| Prince George's County | 8 | 24 |
| Prince William County | 2 | 13 |
| Pulaski County | 3 | 11 |
| Pulaski County | 8 | 29 |
| Pushmataha County | 9 | 71 |
| Putnam County | 2 | 7 |
| Putnam County | 2 | 5 |
| Putnam County | 2 | 7 |
| Putnam County | 2 | 5 |
| Putnam County | 4 | 17 |
| Queen Anne's County | 2 | 5 |
| Quitman County | 3 | 11 |
| Rains County | 2 | 5 |
| Ramsey County | 1 | 4 |
| Randall County | 2 | 45 |
| Randolph County | 2 | 3 |
| Randolph County | 3 | 7 |
| Randolph County | 1 | 2 |
| Rapides Parish | 2 | 3 |
| Rawlins County | 2 | 12 |
| Ray County | 2 | 3 |
| Real County | 1 | 3 |
| Red River County | 5 | 11 |
| Red River Parish | 5 | 18 |
| Refugio County | 1 | 4 |
| Republic County | 1 | 9 |