Locations
| Name | Sites | Samples |
|---|---|---|
| Baxter County | 1 | 1 |
| Bayfield County | 4 | 11 |
| Beaufort County | 2 | 2 |
| Beaufort County | 35 | 144 |
| Beaver County | 8 | 48 |
| Beaver County | 10 | 96 |
| Becker County | 2 | 7 |
| Bedford County | 2 | 3 |
| Bedford County | 1 | 1 |
| Belarus | 5 | 3 |
| Belgium | 169 | 631 |
| Bell County | 57 | 153 |
| Beltrami County | 10 | 19 |
| Bennett County | 1 | 2 |
| Bennington County | 10 | 52 |
| Benson County | 1 | 8 |
| Benton County | 1 | 3 |
| Benton County | 4 | 29 |
| Benzie County | 1 | 3 |
| Berks County | 6 | 19 |
| Bertie County | 2 | 4 |
| Bibb County | 1 | 6 |
| Bienville Parish | 1 | 9 |
| Big Stone County | 1 | 1 |
| Billings County | 2 | 2 |
| Bladen County | 1 | 4 |
| Blaine County | 3 | 6 |
| Blanco County | 1 | 1 |
| Bleckley County | 1 | 6 |
| Blount County | 1 | 2 |