| Mason City to Oswego (Illinois) | 267.85 mi (431.06 km) |
| Mason City to Oswego (New York) | 838.56 mi (1,349.53 km) |
| Mason City to Otsego (Minnesota) | 147.76 mi (237.80 km) |
| Mason City to Ottawa (Illinois) | 255.65 mi (411.43 km) |
| Mason City to Ottawa (Kansas) | 332.26 mi (534.73 km) |
| Mason City to Ottumwa (Iowa) | 152.47 mi (245.37 km) |
| Mason City to Overland (Missouri) | 341.21 mi (549.13 km) |
| Mason City to Overland Park (Kansas) | 304.48 mi (490.01 km) |
| Mason City to Overlea (Maryland) | 903.32 mi (1,453.75 km) |
| Mason City to Oviedo (Florida) | 1,203.17 mi (1,936.31 km) |
| Mason City to Owasso (Oklahoma) | 494.17 mi (795.28 km) |
| Mason City to Owatonna (Minnesota) | 65.14 mi (104.83 km) |
| Mason City to Owensboro (Kentucky) | 490.65 mi (789.63 km) |
| Mason City to Owings Mills (Maryland) | 888.55 mi (1,429.98 km) |
| Mason City to Owosso (Michigan) | 455.35 mi (732.81 km) |
