What is the best way to combine these two sentences? "Washington D.C. is the capital of the United States. It is not part of any of the 50 states."

Although suggests that something is being said "in spite of the fact that," so it makes sense to use it to combine the two sentences since one might think that the capital of the United States should be in one of the 50 states. The other options don't use transition or linking words that make sense.