Maryland is the only U.S. state that uses possessive apostrophes in its county names. Those three counties, Prince George’s County, Queen Anne’s County, and St. Mary’s County, are the only counties among the nation’s more than 3,100 counties and county-equivalents that officially retain possessive apostrophes.
The reason possessive apostrophes are so rare in American place names dates back to the creation of the U.S. Board on Geographic Names (BGN) in 1890, according to a 2016 Mental Floss article. As part of its effort to standardize names on federal maps, the BGN adopted a longstanding policy of removing possessive apostrophes from geographic feature names. Although several explanations have been suggested over the years, the Board has acknowledged that there is no definitive historical record explaining why the policy was originally adopted.
That policy applies primarily to geographic features, such as mountains, rivers, lakes, and valleys, and to the names used on federal maps. It does not govern the official names of administrative entities like counties, which are established under state law.
While most states eventually dropped possessive apostrophes from county names, or never used them in the first place, Maryland preserved its colonial-era names through state law and tradition. As a result, a prince, a queen, and a saint are the only counties in the United States that officially keep their possessive grammar.
