| Harker Heights to Olympia Heights (Florida) | 1,113.04 mi (1,791.27 km) |
| Harker Heights to Omaha (Nebraska) | 710.66 mi (1,143.70 km) |
| Harker Heights to On Top of the World Designated Place (Florida) | 927.29 mi (1,492.32 km) |
| Harker Heights to Onalaska (Wisconsin) | 953.45 mi (1,534.43 km) |
| Harker Heights to Oneida (New York) | 1,461.92 mi (2,352.73 km) |
| Harker Heights to Oneonta (New York) | 1,470.10 mi (2,365.89 km) |
| Harker Heights to Ontario (California) | 1,178.74 mi (1,897.00 km) |
| Harker Heights to Ontario (Oregon) | 1,381.03 mi (2,222.55 km) |
| Harker Heights to Opa-locka (Florida) | 1,113.09 mi (1,791.35 km) |
| Harker Heights to Opelika (Alabama) | 727.97 mi (1,171.56 km) |
| Harker Heights to Opelousas (Louisiana) | 332.19 mi (534.61 km) |
| Harker Heights to Orange (California) | 1,189.90 mi (1,914.97 km) |
| Harker Heights to Orange (Texas) | 239.85 mi (385.99 km) |
| Harker Heights to Orange City (Florida) | 988.74 mi (1,591.23 km) |
| Harker Heights to Orangeburg (South Carolina) | 993.30 mi (1,598.56 km) |
