| Walnut Creek to Olympia (Washington) | 632.96 mi (1,018.65 km) |
| Walnut Creek to Olympia Heights (Florida) | 2,564.69 mi (4,127.47 km) |
| Walnut Creek to Omaha (Nebraska) | 1,397.77 mi (2,249.49 km) |
| Walnut Creek to On Top of the World Designated Place (Florida) | 2,350.52 mi (3,782.79 km) |
| Walnut Creek to Onalaska (Wisconsin) | 1,652.07 mi (2,658.76 km) |
| Walnut Creek to Oneida (New York) | 2,431.73 mi (3,913.49 km) |
| Walnut Creek to Oneonta (New York) | 2,467.80 mi (3,971.54 km) |
| Walnut Creek to Ontario (California) | 364.19 mi (586.11 km) |
| Walnut Creek to Ontario (Oregon) | 498.57 mi (802.37 km) |
| Walnut Creek to Opa-locka (Florida) | 2,563.25 mi (4,125.15 km) |
| Walnut Creek to Opelika (Alabama) | 2,085.66 mi (3,356.54 km) |
| Walnut Creek to Opelousas (Louisiana) | 1,777.25 mi (2,860.21 km) |
| Walnut Creek to Orange (California) | 368.68 mi (593.33 km) |
| Walnut Creek to Orange (Texas) | 1,698.72 mi (2,733.82 km) |
| Walnut Creek to Orange City (Florida) | 2,410.01 mi (3,878.54 km) |
