In case you were asking why it's on the map in the first place, it's because even though it is not a state and was initially forbidden, as the seat of governmen

In case you were asking why it's on the map in the first place, it's because even though it is not a state and was initially forbidden, as the seat of government, to cast votes for the Pres/VP, that changed in 1961 with the 23rd Amendment, which granted DC a number of electoral votes equal to the least populous state. It's interesting to note that the entire South did not ratify the amendment, except Tennessee. Also, DC still does not have separate representation in the Congress. More info: [Wikipedia](https://en.wikipedia.org/wiki/Twenty-third_Amendment_to_the_United_States_Constitution https://en.wikipedia.org/wiki/Twenty-third_Amendment_to_the_...)