Saarland is one of the federal states of modern Germany, with its capital at Saarbrücken. It is comprised of six districts -
Saarland borders France to the south, Luxembourg to the west and the German federal state of Rhineland-Palatinate to the north and east. The population (1,080,000, with a population density of 420 people/km2) is mostly clustered in cities around the French border. The state contains massive coal deposits which have been jealously contested between France and Germany in its various incarnations since they were first developed in the 19th century. France gained control of the region in the 1680s and then relinquished it in 1697, regaining control between 1793 and 1815 in the French Revolutionary Wars. After the Congress of Vienna it was part of the Prussian Rhineland Province, later being a part of the German Empire.
After the Treaty of Versailles, France gained control of the Saar's coal mines for fifteen years so as to extract compensation. After this period had expired a plebiscite was to be held on the region's future, and it overwhelmingly voted ninety per cent in favour of rejoining Nazi Germany. After World War II, during which it suffered heavy bombing as an important part of the German industrial complex, it fell under French control within their zone of occupation. In 1946 it became a separate zone in which the French, forever looking for ways to weaken West Germany, saw the potential for a new state. In 1951 it was granted associate status of the Council of Europe, which was one of the first supranational institutions in Europe which aimed towards integration and remains today the one with the most member states.
The Saar was used as leverage by France in negotiations with West Germany right up to when it the latter was allowed to regain sovereignity of it. One of the West German state's major foreign policy goals (apart from survival) was to regain the Saar because of its economic potential, which meant the issue became contentious between those who wanted a strong West German state and those who wanted an emasculated one. Among the former may be counted the United States of America, which needed Europe to contribute more to defence in the wake of the Korean War. The Franco-German problem, which had plagued Europe for a century, meant that both these two enemies wanted control of the region. Despite co-operation within the European Coal and Steel Community the two states were still not on cordial terms with each other.
In 1947 France had made the Saar a politically autonomous region in economic union with themselves, and ruled it virtually as a colony. The region was overwhelmingly German in character and West Germany would not rest until they got it back. France decided to moot the idea of making the Saar a 'Europeanised' area that would not be ruled by any sovereign state. But when a referendum was held in the Saar in October 1955, 96% of residents voted for incorporation into West Germany. A year later France bowed to the inevitable and this took place. With this issue resolved, Franco-German co-operation was greatly helped along and a possible barrier to further European integration was removed. The Treaty of Rome would come soon afterwards.
Statistics from Wikipedia.