After an emotive campaign harking back to the bitterness of German reunification five years ago, a clear majority in Brandenburg opted for going it alone.
The big city was less insular, but the majority of Berliners looked likely, according to first projections, to fall short of the required 25 per cent of eligible voters. The fusion had been approved by the assemblies of the two regions, but would have required the endorsement of both sets of voters.
The goal of knocking down the last wall was supported by all the big national parties, including the Christian Democrats who dominate Berlin, and Brandenburg's Social Democrats. "For 700 years Berlin and Brandenburg were together, the wartime allies pulled us apart in 1945," declared Manfred Stolpe, Brandenburg's Prime Minister.
The politicians insisted that the merger would save DM1bn (pounds 430m) a year in administrative costs, and increase the unified region's competitiveness against Germany's 14 other states. "If you want to play in the big leagues, you have to join forces," said Berlin's mayor, Eberhard Diepgen. With a joint population of 6 million, Berlin-Brandenburg would have been the fifth largest land in the federal republic.
But age-old grudges, exacerbated in the communist era when West Berlin was walled off from its rural backyard, weighed more heavily on voters than economic rationale.
Apart from the line of minefields that ran through Berlin, there was another kind of division. The communists wanted to turn their half of the city into a showcase, lavishing it with investment and consumer goods at the expense of the countryside.
Now Brandenburgers had a chance to repay the debt. Shunning their leaders' advice, grassroots organisations sprang up with the slogan: "Things are bad enough without Berlin, they will be worse with Berlin".
Unemployment, at 16.4 per cent, is among the highest in Germany, and despite large infusions of capital, Brandenburg's infrastructure is among the least developed.
The referendum also confirmed the ever-growing influence of the Party of Democratic Socialism, the East German post-Communists.
Capturing, once again, the public mood better than the "Wessi"-dominated parties, the PDS produced the winning campaign slogan: "One unification is enough."