Collection place
- Oakland, Alameda County, California1 objects
- Oakley, Contra Costa County, California816 objects
- Oakmont area, Sonoma County, California20 objects
- Oakville area, Napa Valley, Napa County525 objects
- Oceania73 objects
- Ocucaje District, Ica Valley, Ica Region7 objects
- Ocucaje Site A, Ocucaje District, Ica Valley3 objects
- Ocucaje Site E, Ocucaje District, Ica Valley4 objects
- Ohio184 objects
- Oklahoma4 objects
- Olancha (CDP), Inyo County, California18 objects
- Old Airport area, Grand Canyon, Coconino County2 objects
- Old Fort, Upper Piqua, Miami County, Ohio2 objects
- Old Mission Dam, San Diego, San Diego County9 objects
- Orange County, California1 objects
- Orange Free State Province, Republic of South Africa4 objects
- Oregon425 objects
- Orinda, Contra Costa County, California3 objects
- Oro Fino Valley, Siskiyou County, California3 objects
- Oromia Region, Ethiopia3 objects