Washington, D.C was originally supposed to be shaped like a diamond, with roughly 60% of its land area sitting on territory ceded from the state of Maryland and roughly 40% of its territory sitting on land ceded by the state of Virginia, but development of the portion of territory given to the federal government by Virginia was slow to come, and eventually, Virginia asked for the federal government to return its portion - a request that the federal government agreed to honour. Therefore, all of the territory that Washington, D.C, occupies today was once part of the state of Maryland and Maryland borders Washington, D.C. on three sides. Many government agencies and offices can be found in those parts of Virginia directly across the Potomac River from Washington, D.C., in places like Arlington, so Virginia borders Washington, D.C. on its remaining side. The District of Columbia only directly borders those two US states - Maryland and Virginia. The next closest states would be Pennsylvania and Delaware, each of which would probably be about 90 minutes by car from D.C. city limits to the state line.