| Rio Grande City to Olympia (Washington) | 1,937.70 mi (3,118.42 km) |
| Rio Grande City to Olympia Heights (Florida) | 1,147.19 mi (1,846.23 km) |
| Rio Grande City to Omaha (Nebraska) | 1,040.29 mi (1,674.18 km) |
| Rio Grande City to On Top of the World Designated Place (Florida) | 1,027.57 mi (1,653.72 km) |
| Rio Grande City to Onalaska (Wisconsin) | 1,282.44 mi (2,063.89 km) |
| Rio Grande City to Oneida (New York) | 1,738.52 mi (2,797.88 km) |
| Rio Grande City to Oneonta (New York) | 1,740.44 mi (2,800.96 km) |
| Rio Grande City to Ontario (California) | 1,237.50 mi (1,991.57 km) |
| Rio Grande City to Ontario (Oregon) | 1,585.27 mi (2,551.25 km) |
| Rio Grande City to Opa-locka (Florida) | 1,151.09 mi (1,852.51 km) |
| Rio Grande City to Opelika (Alabama) | 916.34 mi (1,474.71 km) |
| Rio Grande City to Opelousas (Louisiana) | 499.45 mi (803.79 km) |
| Rio Grande City to Orange (California) | 1,243.62 mi (2,001.41 km) |
| Rio Grande City to Orange (Texas) | 402.04 mi (647.02 km) |
| Rio Grande City to Orange City (Florida) | 1,086.37 mi (1,748.35 km) |
