| Grant O. Gale Observatory | Iowa | — |
| Granville observatory | Massachusetts | — |
| Grasslands Observatory | Tucson | — |
| Great Basin Bird Observatory | — | — |
 Green Bank Observatory | Condado de Pocahontas | 818 m |
| Greiner Research Observatory | Cross Plains | — |
| Grems Timmons Observatories | Graettinger | — |
| Griffin Hunter Observatory | Bethune-Cookman University | — |
| Guam Magnetic Observatory | — | — |
 Gurley Observatory | Marietta | — |
| Hagerstown observatory | Hagerstown | — |
 Haggart Observatory | Oregón | — |
 Hale Solar Laboratory | California | — |
| Haleakala-LCO Clamshell #3 | Kula | — |
| Haleakala-LCO OGG B #2 | Kula | — |
| Halstead Observatory | Princeton | — |
 Hanging Rock Raptor Observatory | Condado de Monroe | — |
| Hard Labor Creek Observatory | Georgia | — |
| Harken Astronomical Observatory | Pewaukee | — |
| Harlingten Research observatory | Ánimas | — |
 Harquahala Peak Observatory | condado de La Paz | — |
 Hartung–Boothroyd Observatory | Nueva York | — |
 Harvard-Smithsonian Center for Astrophysics | Cambridge | — |
| Harvest Moon observatory | Terre Haute | — |
| Harvest observatory | Harvest | — |
 Hat Creek Radio Observatory | California | — |
| Haverford observatory | Municipio de Haverford | — |
| Hawaii Center for Volcanology | — | — |
| Hawkeye Observatory | Durand | — |
| Hazardous Observatory | Mayhill | — |
| Heartland Observatory | Carmel | — |
| Heaven on Earth Observatory | Weed Lookout Tower | — |
| Hector J. Robinson Observatory | Condado de Wayne | — |
| Hemet observatory | Hemet | — |
 Hereford Arizona Observatory | Arizona | 1.423 m |
| Heron Cove Observatory | Orcas Village | — |
| Herrett Observatory | Idaho | — |
| Hidden Valley Observatory | Dakota del Sur | — |
| High Altitude Observatory | South Kona | — |
| High Point observatory | High Point | — |
| High Resolution Fly's Eye Cosmic Ray Detector | Utah | — |
| Highland Road Park Observatory | Luisiana | — |
| HillTopTop observatory | Edgewood | — |
| HIPAS Observatory | Alaska | — |
 Hirsch Observatory | — | — |
 Holcomb Observatory and Planetarium | Indiana | — |
 Holden Observatory | Siracusa | — |
 Honolulu Magnetic Observatory | Ewa Beach | 4 m |