1. Birth of the District of Columbia: October 1, 1800 marked the birth of the District of Columbia as the new capital of the United States. It was established by an Act of Congress, signed by President John Adams, and named after Christopher Columbus.

2. Landmark Homes: Designed by architect Charles Bullfinch, the Octagon House on New York Ave was completed in 1801, and became famous for hosting James Madison during the decisive Battle of Bladensburg in 1814. A visit to the house is a chance to step back in time and see how affluent Washingtonians lived in the early 19th century.

3. First Presidential Residence: On October 1, 1800, President John Adams moved into the newly-built President's House, which is now known as the White House. This marked the first time a U.S. president had a residence in the new capital.

4. Emancipation Day: Since 2005, DC has observed Emancipation Day on April 16, marking the day in 1862 when President Abraham Lincoln signed the DC Compensated Emancipation Act, ending slavery in the district. However, the date actually refers to October 1, 1862, when the act came into effect.

5. Tragedy at the Navy Yard: On September 16, 2013, Aaron Alexis, a former Navy reservist and defense contractor, perpetrated a mass shooting at the Washington Navy Yard in Southeast DC. The attack left 13 people dead, including the perpetrator, and was one of the deadliest mass shootings in US history at the time. The anniversary, however, falls within the same season as the hallmark of October, Halloween.