Something I never knew, from a George Will column about the prospect of making the District of Columbia a full-fledged state (emphasis added):

The new state probably would promptly enact a commuter tax hitting Maryland and Virginia residents. And, more important, the splendid vistas of the nation's capital might be jeopardized. They are protected by the limits on building heights that Congress mandates. But Congress would have no authority to impose such mandates on the new state. Congress admitted Oklahoma to statehood on the condition that Guthrie remain the state's capital until 1913. But in 1910 Oklahoma made Oklahoma City the capital, and the U.S Supreme Court held that statehood could not be conditioned by limiting a state's sovereign powers. Anyway, 38 state legislatures are unlikely to make of D.C. the only state with no rural interests, and one dominated by a single interest -- the federal government.