| San Marcos to Orangeburg (South Carolina) | 2,085.63 mi (3,356.50 km) |
| San Marcos to Orangevale (California) | 445.40 mi (716.80 km) |
| San Marcos to Orchards (Washington) | 912.75 mi (1,468.93 km) |
| San Marcos to Orcutt (California) | 221.26 mi (356.09 km) |
| San Marcos to Oregon (Ohio) | 1,929.35 mi (3,104.99 km) |
| San Marcos to Oregon (Wisconsin) | 1,646.58 mi (2,649.91 km) |
| San Marcos to Oregon City (Oregon) | 891.30 mi (1,434.42 km) |
| San Marcos to Orem (Utah) | 580.13 mi (933.63 km) |
| San Marcos to Orinda (California) | 432.00 mi (695.24 km) |
| San Marcos to Orland Park (Illinois) | 1,702.70 mi (2,740.23 km) |
| San Marcos to Orlando (Florida) | 2,140.51 mi (3,444.81 km) |
| San Marcos to Ormond Beach (Florida) | 2,137.46 mi (3,439.91 km) |
| San Marcos to Oro Valley (Arizona) | 363.34 mi (584.74 km) |
| San Marcos to Oroville (California) | 502.93 mi (809.38 km) |
| San Marcos to Oshkosh (Wisconsin) | 1,707.00 mi (2,747.15 km) |
