About St. Mary’s

Stats & Facts

St. Mary’s County is situated on a peninsula in Southern Maryland with over 500 miles of shoreline on the Patuxent River, Potomac River and Chesapeake Bay.

The Naval Air Station, Patuxent River, employing 22,400 military, civilians and defense contractors, is home to the U.S. Naval Air Systems Command (NAVAIR), including the Naval Air Warfare Center Aircraft Division (NAWCAD). With over 200 high-tech aerospace and defense contractors, the county has emerged as a world-class center for maritime aviation research, development, testing, evaluation, and acquisition.

From History to High-Tech ... and Everything in Between

The area combines access to technology with a rich heritage and a myriad of outdoor sports and recreational opportunities. The county’s location allows for easy access to major metropolitan areas while offering residents a high quality of life and affordable lifestyles. St. Mary’s County’s 1,990 businesses employ 28,000 workers; an estimated 50 of these businesses have 100 or more workers. Businesses include DynCorp International, Wyle, BAE Systems, SAIC, L-3, Lockheed Martin, Northrop Grumman, and many others. Non-defense employers include St. Mary’s Hospital, St. Mary’s College of Maryland, Burch Oil, and the Paul Hall Center for Maritime Training and Education.

Check out more stats and facts below, or click to view the Brief Economic Facts sheet for St. Mary's County from the Maryland Department of Commerce.

Whether you have come to explore the past, savor the beauty of the moment, or imagine possibilities in the future, you will find that you are always welcome in St. Mary's, Maryland.


  • Yearly Precipitation (inches): 46.2
  • Yearly Snowfall (inches): 14.5
  • Summer Temperature (ºF): 75.3
  • Winter Temperature (ºF): 37.6
  • Duration of Freeze-Free Period (days): 283.6
  • Land Area (square miles): 372.5
  • Water Area (square miles): 37.7
  • Shoreline (miles): 536
  • Elevation (feet) to sea level: 192


  • St. Mary’s County Households (2010): 38,450
  • St. Mary’s County Population (2014): 110,382​
    • Under 5: 7,277 (6.82%)
    • 5 – 19: 23,239 (22.16%)
    • 20 - 44: 36,567 (31.42%)
    • 45 – 64: 30,046 (28.54%)
    • 65 and over: 13,253 (11.04%)
  • Median age: 36.3 years

-Facts from Maryland Department of Commerce


  • Highest percentage of high-tech employment in the region
  • Growth rate 2nd fastest in state 2000-09
  • Annual growth rate 3rd fastest in state
  • 3rd highest birth rate and 6th lowest death rate in state
  • Youngest population in state
  • Highest concentration of military veterans in state
  • Fastest growing workforce in state
  • 3rd highest median household income growth in state
  • 6th lowest unemployment rate in state
  • 14th highest earned income level in the U.S.
  • Leonardtown is the first (and only!) Arts & Entertainment District in Southern Maryland


  • On March 25, 1634, the first Roman Catholic Mass in the English speaking colonies was celebrated on St. Clement’s Island under a hand-hewn cross.
  • Mathias de Sousa, one of the original colonists and an indentured servant, was the first person of African descent to vote. While living at St. Mary’s City, he served in the 1642 legislative assembly of freemen.
  • In 1639, Margaret Brent arrived in the new colony with her sister establishing their own farm: “Sisters Freehold.” On June 24, 1648 she petitioned the assembly for the right to vote. Although she was denied, Margaret Brent is known as the “first suffragette.”
  • In 1649, Maryland’s Act of Religious Toleration was passed. The law recognized freedom of religion in the colonies. This made St. Mary’s the first colony to practice religious toleration.


  • St. Mary’s County is in Southern Maryland.
  • It is a peninsula bounded by the Potomac and Patuxent Rivers and the Chesapeake Bay.
  • St. Mary’s County has approximately 500 miles of shoreline.
  • St. Mary’s County is Maryland’s “Mother County.”
  • Maryland was founded at St. Clement’s Island in 1634.
  • Historic St. Mary’s City was the state’s first colonial capital.
  • St. Mary’s County’s population is 105,151 according to the 2010 U.S. Census, making it 2% of the state population. The number of persons under 19 is 30,795, which is 29% of the county’s population.
  • St. Mary’s County’s average summer temperature is 74°F winter temperature is 37°F with an average snowfall of 17.8 inches.
  • St. Mary’s County’s largest employer is the Patuxent River Naval Air Station, which has nearly 11,000 employees.
  • The county seat is Leonardtown. Founded in 1708, it is one of the oldest county seats in the United States.
  • St. Mary’s County is governed by the Commissioners of St. Mary's County. The board is a five-member group elected for four-year terms.
  • St. Mary’s County is home to an Amish Community of approximately 350 families. The first Amish families arrived from Lancaster County, Pennsylvania, in around 1940.
  • St. Mary’s County is home to the National Oyster Shucking Contest which takes place at the U.S. Oyster Festival each October.
  • St. Mary’s County has its very own dish: Stuffed Ham.