| County : | St. Mary's County |
| State : | Maryland (MD) |
| Land Area : | 357.18 sq mi |
| Water Area : | 407.07 sq mi |
| Latitude : | 38.2226660 |
| Longitude : | -76.5342705 |
| Population (2010): | 105,151 |
| Population Estimate (2012) : | 105,528 |
| Population Density : | 294.39/sq mi |
| Housing Units (2012) : | 41,282 |
| Median Household Income (2012) : | $85,032 (Maryland : $72,999, USA : $53,046) |
| Median Family Income (2012) : | $92,182 (Maryland : $88,092, USA : $64,585) |
| Median House Price (2012) : | $312,100 (Maryland : $304,900, USA : $181,400) |
St. Mary's County Cities / Towns
| California (11,857) | Charlotte Hall (1,420) | Golden Beach (3,796) |
| Leonardtown Town (2,930) | Lexington Park (11,626) | Mechanicsville (1,508) |
| Piney Point (864) | St. George Island (257) | Tall Timbers (462) |
St. Mary's County Zip Codes
| 20606 (431) | 20609 (1,120) | 20618 (607) |
| 20619 (10,503) | 20620 (1,443) | 20621 (1,373) |
| 20622 (4,900) | 20624 (1,282) | 20626 (373) |
| 20628 (594) | 20630 (348) | 20634 (5,927) |
| 20636 (9,937) | 20650 (13,717) | 20653 (24,481) |
| 20659 (23,498) | 20660 (97) | 20667 (494) |
| 20670 (1,014) | 20674 (830) | 20680 (1,119) |
| 20684 (1,125) | 20686 (1,332) | 20687 (313) |
| 20690 (740) | 20692 (1,051) |