| San Marcos to Oskaloosa (Iowa) | 1,456.50 mi (2,344.01 km) |
| San Marcos to Oswego (Illinois) | 1,679.58 mi (2,703.02 km) |
| San Marcos to Oswego (New York) | 2,292.31 mi (3,689.12 km) |
| San Marcos to Otsego (Minnesota) | 1,505.39 mi (2,422.69 km) |
| San Marcos to Ottawa (Illinois) | 1,650.42 mi (2,656.10 km) |
| San Marcos to Ottawa (Kansas) | 1,279.98 mi (2,059.93 km) |
| San Marcos to Ottumwa (Iowa) | 1,463.01 mi (2,354.48 km) |
| San Marcos to Overland (Missouri) | 1,542.30 mi (2,482.09 km) |
| San Marcos to Overland Park (Kansas) | 1,314.16 mi (2,114.94 km) |
| San Marcos to Overlea (Maryland) | 2,286.19 mi (3,679.27 km) |
| San Marcos to Oviedo (Florida) | 2,145.40 mi (3,452.68 km) |
| San Marcos to Owasso (Oklahoma) | 1,229.02 mi (1,977.91 km) |
| San Marcos to Owatonna (Minnesota) | 1,489.81 mi (2,397.62 km) |
| San Marcos to Owensboro (Kentucky) | 1,714.06 mi (2,758.51 km) |
| San Marcos to Owings Mills (Maryland) | 2,271.47 mi (3,655.58 km) |
