| Fort Madison to Oswego (Illinois) | 173.12 mi (278.60 km) |
| Fort Madison to Oswego (New York) | 785.59 mi (1,264.29 km) |
| Fort Madison to Otsego (Minnesota) | 340.82 mi (548.50 km) |
| Fort Madison to Ottawa (Illinois) | 141.12 mi (227.11 km) |
| Fort Madison to Ottawa (Kansas) | 250.71 mi (403.48 km) |
| Fort Madison to Ottumwa (Iowa) | 62.26 mi (100.19 km) |
| Fort Madison to Overland (Missouri) | 142.83 mi (229.87 km) |
| Fort Madison to Overland Park (Kansas) | 213.87 mi (344.19 km) |
| Fort Madison to Overlea (Maryland) | 789.03 mi (1,269.82 km) |
| Fort Madison to Oviedo (Florida) | 1,006.85 mi (1,620.37 km) |
| Fort Madison to Owasso (Oklahoma) | 385.09 mi (619.75 km) |
| Fort Madison to Owatonna (Minnesota) | 258.27 mi (415.65 km) |
| Fort Madison to Owensboro (Kentucky) | 300.83 mi (484.14 km) |
| Fort Madison to Owings Mills (Maryland) | 774.05 mi (1,245.72 km) |
| Fort Madison to Owosso (Michigan) | 404.13 mi (650.38 km) |
