1) On May 12, 1784, the town of Baltimore was officially incorporated by the Maryland General Assembly. Baltimore would go on to become one of the most important cities in the United States, playing a significant role in the country's history and economy.

2) On May 12, 1817, the first steamboat to operate in Chesapeake Bay, the "Maryland," began service. The boat was built by local inventor John O. Turnbull and helped establish Baltimore as an important trade port.

3) May 12, 1844 marked the founding of the Maryland Historical Society, a nonprofit organization dedicated to preserving and celebrating the state's history. The society maintains a museum and library in Baltimore and hosts exhibits, lectures, and events throughout the year.

4) On May 12, 1971, Maryland governor Marvin Mandel signed a bill into law establishing a state lottery. The lottery has since become a popular form of gambling in Maryland, generating millions of dollars in revenue each year for education, health care, and other state programs.

5) May 12, 2008 saw the opening of the Green Line on the Washington Metro, which extended the rail system to new areas of Maryland beyond Washington, D.C. The Green Line connects Prince George's County to downtown D.C. and features stops at notable landmarks such as the University of Maryland and the National Archives.