1. On April 13, 1664, the Maryland General Assembly passed a law granting freedom to any slave who converted to Christianity. This law would eventually be overturned in 1715, setting the stage for the legalization of slavery in Maryland.

2. On April 13, 1748, the town of Havre de Grace was founded in Harford County, Maryland. Originally settled as a small fishing village, Havre de Grace became an important port town in the 19th century and played a critical role in the War of 1812.

3. On April 13, 1861, the Maryland State House was the site of a crucial debate on the issue of whether Maryland would secede from the Union. The state ultimately decided to stay with the Union, but its residents remained deeply divided throughout the Civil War.

4. On April 13, 1945, the USS Frederick was commissioned at the Bethlehem Steel Shipyard in Baltimore, Maryland. The Frederick served as a supply ship during World War II and was eventually decommissioned in 1960.

5. On April 13, 1970, Maryland Governor Marvin Mandel signed a law decriminalizing the possession of small amounts of marijuana. This made Maryland one of the first states in the country to take steps towards legalizing marijuana, although it would take several more decades for full legalization to become a reality.