Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| One Hundred and One Ranch | Locale | 262 | San Benito | 36 37 35 N | 121 13 56 W |
| One Hundred and Twenty Canal | Canal | 38 | Alameda | 37 46 33 N | 121 33 60 W |
| One Hundred Dollar Mine | Mine | 1928 | Siskiyou | 41 19 33 N | 123 06 23 W |
| One Hundred Eighteenth Street Elementary School | School | 42 | Los Angeles | 33 55 33 N | 118 16 19 W |
| One Hundred Eighty-Sixth Street School | School | 17 | Los Angeles | 33 51 46 N | 118 18 22 W |
| One Hundred Eleventh Street School | School | 30 | Los Angeles | 33 56 03 N | 118 14 44 W |
| One Hundred Fifty-Sixth Street Elementary School | School | 15 | Los Angeles | 33 53 19 N | 118 19 03 W |
| One Hundred Fifty-Third Street Elementary School | School | 16 | Los Angeles | 33 53 36 N | 118 18 18 W |
| One Hundred Ninth Street Elementary School | School | 30 | Los Angeles | 33 56 13 N | 118 15 42 W |
| One Hundred Ninth Street Recreation Center | Park | 31 | Los Angeles | 33 56 10 N | 118 14 55 W |
| One Hundred One Mine | Mine | 1876 | Sierra | 39 34 48 N | 120 35 08 W |
| One Hundred Palms | Populated Place | -20 | Riverside | 33 33 43 N | 116 10 21 W |
| One Hundred Second Street Childrens Center | Building | 33 | Los Angeles | 33 56 40 N | 118 14 17 W |
| One Hundred Second Street Elementary School | School | 33 | Los Angeles | 33 56 35 N | 118 14 16 W |
| One Hundred Seventh Street Elementary School | School | 37 | Los Angeles | 33 56 23 N | 118 16 20 W |
| One Hundred Sixteenth Street Elementary School | School | 34 | Los Angeles | 33 55 44 N | 118 15 41 W |
| One Hundred Third Street Baptist Church | Church | 33 | Los Angeles | 33 56 34 N | 118 14 08 W |
| One Hundred Thirty-Fifth Street Elementary School | School | 30 | Los Angeles | 33 54 33 N | 118 17 22 W |
| One Hundred Thirty-Ninth Street School | School | 35 | Los Angeles | 33 54 19 N | 118 15 37 W |
| One Hundred Twelfth Street Elementary School | School | 30 | Los Angeles | 33 56 00 N | 118 15 09 W |
| One Hundred Twenty-Second Street Elementary School | School | 40 | Los Angeles | 33 55 18 N | 118 16 03 W |
| One Mile Spring | Spring | 1358 | Trinity | 41 05 56 N | 123 26 11 W |
| One Suerte | Civil | 8 | Monterey | 36 40 47 N | 121 44 36 W |
| One Thousand Eight Hundred Eighty One Ditch | Canal | 88 | Fresno | 36 32 33 N | 119 39 36 W |
| One Thousand Steps | Locale | 15 | Santa Barbara | 34 23 45 N | 119 42 49 W |
| One Union Square Shopping Center | Locale | 18 | San Francisco | 37 47 15 N | 122 24 23 W |
| Oneeyed Flat | Flat | 761 | Trinity | 41 05 32 N | 122 42 26 W |
| Onehundred Acre Prairie | Area | 657 | Humboldt | 41 06 19 N | 123 46 26 W |
| Oneida Creek | Stream | | Amador | 38 22 02 N | 120 46 31 W |
| Oneida Lake | Lake | 2947 | Mono | 37 59 39 N | 119 15 06 W |
| Oneida Mine | Mine | 434 | Amador | 38 22 24 N | 120 47 17 W |
| Oneill Dam | Dam | 56 | Merced | 37 05 24 N | 121 02 22 W |
| Oneill Forebay Dike Dam | Dam | 70 | Merced | 37 06 48 N | 121 03 16 W |
| Onemile Bridge | Bridge | 310 | San Luis Obispo | 35 23 19 N | 120 34 56 W |
| Onemile Camp | Locale | 1390 | Trinity | 41 06 00 N | 123 26 11 W |
| Onemile Creek | Stream | | Colusa | 39 23 20 N | 122 03 13 W |
| Onemile Creek | Stream | | Siskiyou | 41 34 21 N | 123 22 40 W |
| Onemile Lake | Lake | 1752 | Siskiyou | 41 32 39 N | 123 20 23 W |
| Oneonta Elementary School | School | 175 | Los Angeles | 34 06 06 N | 118 09 10 W |
| Oneonta School | School | 8 | San Diego | 32 34 21 N | 117 06 42 W |
| Oneonta Slough | Gut | 3 | San Diego | 32 33 55 N | 117 07 52 W |
| Oneonto Congregational Church | Church | 177 | Los Angeles | 34 06 30 N | 118 08 15 W |
| Oneto Ranch | Locale | 554 | Amador | 38 26 27 N | 120 44 17 W |
| Onion Butte | Summit | 1771 | Tehama | 40 12 05 N | 121 34 04 W |
| Onion Camp | Locale | 1542 | Trinity | 40 57 35 N | 123 27 05 W |
| Onion Creek | Stream | | El Dorado | 38 51 21 N | 120 32 10 W |
| Onion Creek | Stream | | Inyo | 37 09 24 N | 118 24 03 W |
| Onion Creek | Stream | | Placer | 39 15 15 N | 120 22 20 W |
| Onion Creek | Stream | | Plumas | 39 37 05 N | 121 02 45 W |
| Onion Creek | Stream | | Shasta | 40 27 28 N | 121 44 12 W |
| Onion Creek | Stream | | Shasta | 40 54 33 N | 122 34 33 W |
| Onion Creek | Stream | | Sierra | 39 31 45 N | 120 17 32 W |
| Onion Creek Campground | Locale | 1834 | Placer | 39 16 29 N | 120 21 48 W |
| Onion Creek Experimental Forest | Park | 1964 | Placer | 39 16 56 N | 120 20 58 W |
| Onion Creek Ridge | Ridge | 1362 | Shasta | 40 55 24 N | 122 34 20 W |
| Onion Flat | Flat | 1997 | El Dorado | 38 59 13 N | 120 13 29 W |
| Onion Flat | Flat | 1684 | Plumas | 40 04 19 N | 121 01 42 W |
| Onion Flat | Flat | 1859 | Siskiyou | 41 57 18 N | 123 00 31 W |
| Onion Lake | Lake | 1358 | Humboldt | 41 22 42 N | 123 44 57 W |
| Onion Lake | Lake | 3179 | Tuolumne | 38 02 33 N | 119 19 10 W |
| Onion Meadow | Flat | 1935 | Siskiyou | 41 08 49 N | 122 59 12 W |
| Onion Meadow | Flat | 2466 | Tulare | 36 01 59 N | 118 35 59 W |
| Onion Meadow Peak | Summit | 2529 | Tulare | 36 01 40 N | 118 36 10 W |
| Onion Mountain | Summit | 1443 | Humboldt | 41 22 22 N | 123 44 59 W |
| Onion Patch Gulch | Valley | | Mendocino | 39 11 23 N | 123 36 05 W |
| Onion Pond (historical) | Lake | 171 | Sonoma | 38 34 13 N | 123 06 31 W |
| Onion Spring | Spring | 1573 | Siskiyou | 41 31 41 N | 122 04 00 W |
| Onion Spring Meadow | Flat | 2401 | Fresno | 37 24 03 N | 119 04 16 W |
| Onion Springs | Spring | 2084 | Shasta | 40 29 43 N | 121 34 36 W |
| Onion Springs | Spring | 1636 | Tehama | 39 54 39 N | 122 49 20 W |
| Onion Summit | Summit | 1698 | Tehama | 40 12 41 N | 121 34 57 W |
| Onion Valley | Basin | 2700 | Inyo | 36 46 27 N | 118 19 57 W |
| Onion Valley | Flat | 2169 | Amador | 38 34 01 N | 120 11 23 W |
| Onion Valley | Locale | 1918 | Plumas | 39 47 45 N | 120 52 55 W |
| Onion Valley | Valley | | Calaveras | 38 25 55 N | 120 04 09 W |
| Onion Valley | Valley | | Placer | 39 15 07 N | 120 39 15 W |
| Onion Valley | Valley | | Sierra | 39 31 16 N | 120 17 13 W |
| Onion Valley Campground | Locale | 2810 | Inyo | 36 46 17 N | 118 20 24 W |
| Onion Valley Creek | Stream | | Plumas | 39 48 30 N | 121 02 40 W |
| Onion Valley Reservoir | Reservoir | 1913 | Plumas | 39 47 36 N | 120 52 47 W |
| Onion Valley Spring Two | Civil | 308 | Merced | 37 03 57 N | 121 11 34 W |
| Onion Valley Spring Two | Spring | 1416 | Placer | 39 15 25 N | 120 39 10 W |
| Onizuka Park | Park | 710 | Kern | 34 54 59 N | 117 55 15 W |
| Ono | Populated Place | 295 | Shasta | 40 28 31 N | 122 37 05 W |
| Onstott Ranch | Locale | 31 | Butte | 39 22 54 N | 121 39 44 W |
| Ontario | Populated Place | 306 | San Bernardino | 34 03 48 N | 117 39 03 W |
| Ontario Army Air Field (historical) | Military (Historical) | 281 | San Bernardino | 34 03 20 N | 117 36 05 W |
| Ontario Christian High School | School | 256 | San Bernardino | 34 02 00 N | 117 39 57 W |
| Ontario Christian High School | School | 267 | San Bernardino | 34 02 21 N | 117 39 00 W |
| Ontario Christian Reformed Church | Church | 260 | San Bernardino | 34 02 03 N | 117 38 57 W |
| Ontario City Library | Building | 309 | San Bernardino | 34 03 58 N | 117 38 56 W |
| Ontario High School | School | 266 | San Bernardino | 34 02 23 N | 117 39 56 W |
| Ontario Home Furnishings Shopping Center | Locale | 252 | San Bernardino | 34 01 55 N | 117 35 33 W |
| Ontario Hospital | Hospital | 315 | San Bernardino | 34 04 09 N | 117 38 31 W |
| Ontario Hot Springs | Spring | 10 | San Luis Obispo | 35 10 50 N | 120 42 11 W |
| Ontario International Airport | Airport | 282 | San Bernardino | 34 03 21 N | 117 36 07 W |
| Ontario Mills Shopping Center | Locale | 308 | San Bernardino | 34 04 15 N | 117 33 03 W |
| Ontario Motor Speedway | Locale | 307 | San Bernardino | 34 04 21 N | 117 33 58 W |
| Ontario Park | Park | 266 | Riverside | 33 51 33 N | 117 35 33 W |
| Ontario Peak | Summit | 2640 | San Bernardino | 34 13 40 N | 117 37 26 W |
| Ontario Peak Trail | Trail | 2536 | San Bernardino | 34 13 55 N | 117 36 38 W |
| Ontario Plaza Shopping Center | Locale | 268 | San Bernardino | 34 02 23 N | 117 39 07 W |
| Ontario Plaza Shopping Center | Locale | 334 | San Bernardino | 34 04 43 N | 117 40 08 W |
| Ontario Reservoir Number 1 | Reservoir | 367 | San Bernardino | 34 05 38 N | 117 38 26 W |
| Ontario Schools Administration Building | Building | 313 | San Bernardino | 34 04 03 N | 117 40 00 W |
| Ontario Village Shopping Center | Locale | 306 | San Bernardino | 34 03 50 N | 117 39 39 W |
| Ontario Vineyard Marketplace Shopping Center | Locale | 255 | San Bernardino | 34 01 59 N | 117 36 43 W |
| Ontario-Upland Sewage Disposal | Locale | 253 | San Bernardino | 34 01 55 N | 117 36 05 W |
| Ontiveros Cemetery | Cemetery | 223 | Santa Barbara | 34 53 23 N | 120 14 01 W |
| Ontop Mine | Mine | 1588 | Plumas | 39 49 31 N | 121 09 35 W |