Why is Washington, DC not a state?

ON A LIST of American states and territories ordered by area, Washington, DC is at the very bottom: nearly 10,000 Washingtons could fit into Alaska. Reorder that list by federal taxes paid per person, and Washington finishes first. But unlike residents of the 50 states, Washingtonians are unrepresented in Congress. They have no senators, and just one non-voting House delegate—Eleanor Holmes Norton, who has held the job for 30 years. Washingtonians could not vote in presidential elections until 1964. Not until 1974 were they permitted to elect their own municipal government, and the city still cannot pass laws or even an annual budget without Congressional review. Its residents are tiring of this arrangement. In a referendum in 2016, 85% of them said they wanted statehood. On March 22nd the House Committee on Oversight and Reform will hold a hearing on the idea. Why have Washingtonians been stateless for so long?