 BGSU Observatory | Bowling Green | — |
 Big Bear Solar Observatory | California | 2.060 m |
| Big Cypress Observatory | Fort Lauderdale | — |
| Big Water observatory | Big Water | — |
| Biosphere 2 Observatory | Arizona | — |
| Bird Conservancy of the Rockies | — | — |
| Bixhoma observatory | Bixby | — |
| BKH Observatory | Fearrington Village | — |
| Black Forest Observatory | Colorado | — |
| Black Moshannon Observatory | Pensilvania | — |
| Black Mountain Observatory | Los Altos Hills | — |
| Black Swamp Bird Observatory | Oak Harbor | — |
| Blackberry Observatory | Port Allen | — |
| BlackBird observatory | Weed Lookout Tower | — |
| BlackCAT | — | — |
| Blue Canyon observatory | Blue Canyon | — |
| Blue Mesa Observatory | New Mexico | — |
| Boca Raton Observatory | Boca Raton | — |
 Boswell Observatory | Nebraska | — |
| Boulder Geomagnetic Observatory | Boulder | — |
| Boulder Knolls observatory | Hidden Meadows | — |
| Boulder Magnetic Observatory | — | — |
 Bowman Observatory | Connecticut | — |
 Brackett Observatory | Claremont | — |
| Bradley Observatory | Georgia | — |
| Bradstreet Observatory | Pensilvania | — |
| Braeside Observatory | Flagstaff | 2.152 m |
| Brooks Astronomical Observatory | Míchigan | — |
| Brooks Observatory | Ohio | — |
 BRRISON | — | — |
| Bucknell Observatory | Pensilvania | — |
 Buehler Planetarium and Observatory | Davie | — |
| Burleith Observatory | Washington D. C. | — |
| Burlington observatory | Nueva Jersey | — |
| Burlington remote site Observatory | Nueva Jersey | — |
| Burnt Tree Hill Observatory | Bristol | — |
 Burrell Memorial Observatory | Ohio | — |
| Byrne observatory | Río Santa Ynez | — |
| C. E. K. Mees Observatory | Nueva York | — |
| CACTUS | — | 610 m |
 Calais Observatory | Calais | — |
 Calvin College Observatory | Grand Rapids | — |
| Calvin M. Hooper Memorial observatory | Hyde Park | — |
| Calvin-Rehoboth Robotic Observatory | Rehoboth | — |
| Camarillo observatory | California | — |
| Canvas View New Mexico Skies observatory | Mayhill | — |
| Capilla Peak Observatory | New Mexico | — |
| Carbuncle Hill observatory | Greene | — |