National Mutual Insurance Company is a District of Columbia corporation. It brought a diversity action in the U.S. District Court of Maryland against Tidewater Transfer Company, a Virginia corporation doing business in Maryland. National Mutual contends that, for diversity purposes, a D.C. resident may file suit against the resident of a state. Tidewater Transfer disagrees. What should be taken into consideration in deciding whether the District of Columbia can, for diversity purposes, be regarded as a state?