Maryland can't make-up it's mind, historically. I always heard it was considered the "Mason-Dixon Line" state, but apparently there are more. From
http://www.mdkidspage.org/History.htmThe Old Line State: This nickname is, according to some, a reference to the Maryland soldiers who fought courageously in the Revolutionary War, the Maryland Line. It is said that General George Washington referred to these soldiers as "The Old Line." Maryland was the only state that had regular troops "of the line" and these soldiers were ranked among the finest and best disciplined in the army. Another origin is given that goes back further in history. It is said that Maryland is referred to as "The Old Line State" because it was the dividing line between the land grants given to William Penn and Lord Baltimore.
The Free State: This nickname originated in an article written by Hamilton Owens, the editor or the Baltimore Sun. In 1923, a Georgia Congressman, William D. Upshaw, attacked Maryland as a traitor to the union because it never passed a State enforcement act supporting Prohibition. Hamilton Owens' article, "The Maryland Free State" was a mocking response to Mr. Upshaw, suggesting that Maryland should secede from the Union before acting to prohibit the sale of liquor. This article was never published but Mr. Owens referred to Maryland as "The Free State" in later editorials.
The Cockade State: This nickname, coined during the Revolutionary War, again refers to the Maryland soldiers. According to King's Handbook of the United States, 1891, the Maryland Old Line was made up of young men who "...wore brilliant cockades". Cockades are badge-like ornaments usually worn on hats. These decorations gave birth to Maryland's nickname, "The Cockade State."
The Monumental State: In the early 17th century, Baltimore was given the nickname of "The Monumental City" and this nickname was transferred to the state over time. "The Monumental City" was bestowed upon Baltimore by President John Quincy Adams, probably in reference to the monuments he saw on his visit to the city in 1827. The "Battle Monument" honoring Baltimore's defensive victory in the War of 1812 was standing on the site of the old court house. Construction was under way on the first major memorial to George Washington. President Adams was also taken to North Point to view the Aquila Randall Monument erected to honor a member of the First Mechanical Volunteers of the Fifth Regiment who was killed on September 12, 1814.