| Santo Tirso to Olympia Heights (Florida) | 4,158.71 mi (6,692.80 km) |
| Santo Tirso to Omaha (Nebraska) | 4,329.08 mi (6,966.98 km) |
| Santo Tirso to On Top of the World Designated Place (Florida) | 4,126.97 mi (6,641.72 km) |
| Santo Tirso to Onalaska (Wisconsin) | 4,024.60 mi (6,476.98 km) |
| Santo Tirso to Oneida (New York) | 3,345.60 mi (5,384.22 km) |
| Santo Tirso to Oneonta (New York) | 3,334.04 mi (5,365.63 km) |
| Santo Tirso to Ontario (California) | 5,559.48 mi (8,947.11 km) |
| Santo Tirso to Ontario (Oregon) | 5,063.56 mi (8,149.02 km) |
| Santo Tirso to Opa-locka (Florida) | 4,147.53 mi (6,674.80 km) |
| Santo Tirso to Opelika (Alabama) | 4,147.49 mi (6,674.74 km) |
| Santo Tirso to Opelousas (Louisiana) | 4,557.37 mi (7,334.38 km) |
| Santo Tirso to Orange (California) | 5,579.67 mi (8,979.61 km) |
| Santo Tirso to Orange (Texas) | 4,655.04 mi (7,491.56 km) |
| Santo Tirso to Orange City (Florida) | 4,083.06 mi (6,571.04 km) |
| Santo Tirso to Orangeburg (South Carolina) | 3,894.96 mi (6,268.34 km) |
