1. On December 18, 1787, Maryland became the 7th state to ratify the United States Constitution, which established the framework for the federal government we know today.

2. On December 18, 1865, the 13th Amendment to the Constitution was ratified, abolishing slavery and involuntary servitude throughout the United States. Maryland was a slave state before the Civil War, but had already abolished slavery in its own state constitution in 1864.

3. The Baltimore and Ohio Railroad, one of the oldest railroads in the country, completed its first passenger train journey from Baltimore to Ellicott's Mills on December 18, 1830. This marked a new era in transportation in Maryland and paved the way for further expansion of the railroad industry.

4. The Chesapeake Bay Bridge-Tunnel, connecting Maryland's eastern shore to Virginia, opened to traffic on December 18, 1964 after five years of construction. The bridge-tunnel spans 17.6 miles and is one of the longest in the world.

5. On December 18, 2015, Maryland Governor Larry Hogan announced $135 million in funding to build a new medical center at the University of Maryland, Baltimore. The new facility will focus on cutting-edge medical research and treatment, and is expected to attract top talent and lead to economic growth in the state.