1. On March 12, 1868, the U.S. Congress passed the District of Columbia Organic Act, which granted D.C. residents the right to vote for local officials and established a territorial government for the district.

2. The U.S. Army Signal Corps was established on March 12, 1860, with the mission of signaling important messages across long distances using flag, light, and sound signals.

3. On March 12, 1912, the District of Columbia became the first jurisdiction in the United States to pass a law requiring automobiles to have license plates.

4. The National Gallery of Art was established in Washington, D.C., on March 12, 1937, with a gift from financier and art collector Andrew W. Mellon.

5. The Washington Monument, an iconic landmark on the National Mall, was dedicated on March 12, 1885, after 30 years of construction. Standing at 555 feet tall, it was the tallest structure in the world at that time.