| Castelo Branco to Olympia Heights (Florida) | 4,226.93 mi (6,802.59 km) |
| Castelo Branco to Omaha (Nebraska) | 4,428.50 mi (7,126.98 km) |
| Castelo Branco to On Top of the World Designated Place (Florida) | 4,202.14 mi (6,762.68 km) |
| Castelo Branco to Onalaska (Wisconsin) | 4,124.60 mi (6,637.90 km) |
| Castelo Branco to Oneida (New York) | 3,437.86 mi (5,532.71 km) |
| Castelo Branco to Oneonta (New York) | 3,425.08 mi (5,512.14 km) |
| Castelo Branco to Ontario (California) | 5,663.81 mi (9,115.03 km) |
| Castelo Branco to Ontario (Oregon) | 5,173.53 mi (8,326.00 km) |
| Castelo Branco to Opa-locka (Florida) | 4,215.95 mi (6,784.91 km) |
| Castelo Branco to Opelika (Alabama) | 4,230.23 mi (6,807.90 km) |
| Castelo Branco to Opelousas (Louisiana) | 4,642.22 mi (7,470.93 km) |
| Castelo Branco to Orange (California) | 5,683.96 mi (9,147.45 km) |
| Castelo Branco to Orange (Texas) | 4,740.63 mi (7,629.31 km) |
| Castelo Branco to Orange City (Florida) | 4,157.11 mi (6,690.23 km) |
| Castelo Branco to Orangeburg (South Carolina) | 3,975.64 mi (6,398.17 km) |
