Why was District of Columbia separate from the United States?

Eople beleived that they were independent and so for thaty they seperated.

Because when the country was founded The founders that the capital city of the country should exist independent from Any state government to achieve this, they Katie and capital District river the District of Columbia. This district, has an automatic runs Washington DC and has most of its laws passed by the federal congress which has supreme authority over any actions of the city government.