1. In 1800, the District of Columbia became the new capital of the United States, replacing Philadelphia. This move was made as part of the District's creation under the 1800 Residence Act, which established a federal district for the purpose of establishing the national capital.

2. In 1864, the American Civil War saw one of its bloodiest battles take place just outside of the District of Columbia. Known as the Battle of Fort Stevens, it was the only time during the war that Confederate forces made an attempt to capture the capital. Although the Union ultimately repelled the attack, President Abraham Lincoln himself came under fire from enemy troops during the battle.

3. In 1927, the Holland Tunnel opened in New York City, connecting Manhattan to New Jersey via an underground tunnel. The project was designed by engineer Clifford Holland, who was born in the District of Columbia. The tunnel was a major engineering feat at the time, and remains a crucial transportation link for the region to this day.

4. In 1959, President Dwight D. Eisenhower signed a bill into law that officially designated Alaska and Hawaii as the 49th and 50th states in the Union, respectively. The bill was signed in Washington D.C., making November 15 a significant day in the history of the District and the country as a whole.

5. In 2013, the District of Columbia made history by becoming one of the first jurisdictions in the United States to legalize recreational marijuana use. The law went into effect on November 15 of that year, allowing adults over the age of 21 to possess and use small amounts of cannabis without fear of prosecution. However, it is important to note that the law does not allow for the sale or distribution of marijuana, so users must obtain it through other means.