ON APRIL 15th the District of Columbia celebrated Emancipation Day, which commemorates Abraham Lincoln’s 1862 order freeing slaves held in Washington, DC. This year, Muriel Bowser, the city’s mayor, used the occasion to announce her plans for a city-wide referendum on making the District a state. The referendum is a new tactic in a decades-long push for statehood. Why is the District seeking statehood now?

Washington’s legal status is unique within America. When the nation was founded, its statesmen worried that if the capital were situated within a state, that state might exercise undue power over the national government. Consequently, the constitution allows for the creation of “a district, not exceeding ten miles square” for the capital, and grants Congress complete authority over this capital district. The resultant District of Columbia was formed out of parts of Maryland and Virginia (although Virginia’s part was eventually returned). Ever since, Washington has been governed by Congress, directly or indirectly. Not being a state, it was entitled to neither representation in Congress nor to vote for president.

When it was formed, the District was home to only about 14,000 people, but as the federal government grew, so did the city. By 1950 it contained more than 800,000 people. Moreover, its residents are largely African-American, and the lack of representation was seen as a civil rights issue. In 1961, a constitutional amendment granted DC residents the right to vote in presidential elections. Congress followed this with limited home rule for the city, but a 1980 effort to grant legislative representation and many other rights of statehood stalled, and the District’s position has changed little since. The federal government continues to have authority over the city’s budget, inviting all manner of meddling from legislators who have sought to change everything from the city’s drug policies to the way its taxis set their fares. Mayor Bowser has seen progress: a court victory in March will allow her government to pass its own budget for the first time, although Congress may still alter it. But despite strong local support (a Washington Post poll last year showed two-thirds of residents support statehood), the prospects of remain slim.

Ms. Bowser’s referendum, should it proceed, will be non-binding: only Congress can grant the District greater representation. This it is loath to do. Washingtonians are overwhelmingly Democrats: since gaining a say in presidential elections, the District has backed a Democrat every time; President Obama carried 91% of its votes in 2012. Republican majorities in Congress are unenthusiastic about creating reliably Democratic seats. Critics also argue that, although DC is more populous than two states (Vermont and Wyoming), it occupies a tiny area, is entirely urban, and dominated by the federal workforce, giving its representatives unusual concerns. Opponents often offer “retrocession” as an alternative—that is, returning the District to the state of Maryland. But politicians in both places are cool about this idea: Washington would become Maryland’s largest city, and its return would substantially alter the state’s political landscape and the District’s identity. It is likely that the motto on Washington’s license plates, “Taxation Without Representation”, will apply for some time to come.