1. On July 21, 1861, the First Battle of Bull Run (also known as First Manassas) took place during the American Civil War. Confederate forces under General Thomas "Stonewall" Jackson routed Union troops in a chaotic and bloody battle that marked the beginning of a long and devastating conflict.

2. On July 21, 1922, the first airplane to fly over the North Pole landed in Teller, Alaska. The Arctic Explorer, piloted by Lt. Albert Cushing Read and carrying the famous explorer Roald Amundsen, made the historic journey from Spitsbergen, Norway to Teller in just over 15 hours.

3. In 1976, the streets of Baltimore were filled with fans celebrating the bicentennial of the United States. The city hosted a parade and a concert featuring the Baltimore Symphony Orchestra, and fireworks lit up the sky over the Inner Harbor. It was a festive and patriotic day for Marylanders.

4. On July 21, 1904, the Olympic Games officially opened in St. Louis, Missouri. Maryland athlete Francis Field would go on to win two gold medals in the track and field events, in the 4x400m relay and the 400m hurdles.

5. In 1923, the Chesapeake Bay Bridge-Tunnel Commission was established to study the feasibility of building a bridge-tunnel system to connect Virginia and Maryland across the Chesapeake Bay. The project would take decades of planning and construction, finally opening in 1964 and revolutionizing transportation between the two states.