| Palmer Divide Observatory | Colorado Springs | — |
| Palo Alto observatory | Palo Alto | — |
| Palomar Mountain-DSS | Palomar Mountain | — |
| Palominas Observatory | Sierra Vista Southeast | — |
 Pan-STARRS | Maui County | — |
 Pandora | — | — |
 Paul Robinson Observatory | Municipio de Lebanon | — |
 Peach Mountain Observatory | Míchigan | — |
| Pear Tree observatory | Valparaiso | — |
| Perkins Observatory | Delaware | — |
| Petit Jean Mountain observatory | Petit Jean Mountain | — |
| Phillips Academy Observatory | Andover | — |
| Phoebe Waterman Haas Public Observatory | Washington D. C. | — |
| Pin Oak Observatory | Fort Madison | — |
 Pine Mountain Observatory | Oregón | — |
| Pineapple Observatory | Frederick | — |
| Pinto Valley observatory | San Bernardino County | — |
| Platteville Atmospheric Observatory | Colorado | — |
| Pleasant Groves Observatory | Pleasant Groves | — |
| Pleasanton observatory | Pleasanton | — |
| Portage Lake Observatory | Míchigan | — |
| Poway Valley observatory | Poway | — |
| Powell Observatory | Kansas | — |
| Prairie Grass Observatory | Mulberry | — |
| Prairie Observatory | — | — |
| Preston Hills observatory | Celina | — |
 Principia Astronomical Observatory | Misuri | — |
| Prude Ranch observatory | Texas | — |
| PSU Greenbush Observatory | Greenbush | — |
 Puckett Observatory | Georgia | — |
 PUNCH-NFI | — | — |
 PUNCH-WFI 1 | — | — |
| PUNCH-WFI 2 | — | — |
| PUNCH-WFI 3 | — | — |
| Putman Mountain Observatory | Loyal Valley | — |
| Rainwater Observatory and Planetarium | Misisipi | — |
| Ralph A. Worley Observatory | Luisiana | — |
| Rancho Del Sol observatory | Camino | — |
| Rancho Palos Verdes observatory | Rancho Palos Verdes | — |
| Rand II Observatory | Lake Placid | — |
| Rand Observatory | Nueva York | — |
| Rani Observatory | San Diego | — |
| Rapid City observatory | Rapid City | — |
| RASC Observatory | Alder Springs | — |
| Rattle Snake Observatory | Smithton | — |
| Red Barn Observatory | Georgia | — |
| Red Buttes Observatory | Laramie | 2.246 m |
| Red de Vigilancia Espacial de los Estados Unidos | Maui County | — |