wikipedia said:http://en.wikipedia.org/wiki/Bonn
During World War II, Bonn had some military significance due to its population.
Following World War II, Bonn was in the British zone of occupation, and in 1949 became the capital of West Germany. The choice of Bonn was made mainly due to the advocacy of Konrad Adenauer, a former Cologne Mayor and Chancellor of West Germany after World War II, who came from that area, despite the fact that Frankfurt already had most of the required facilities and using Bonn was estimated to be 95 Mill DM more expensive than using Frankfurt. Because of its relatively small size for a capital city, Bonn was sometimes referred to, jokingly, as the Bundeshauptstadt ohne nennenswertes Nachtleben (Federal capital with no night-life worthy of the name) or the 'Bundesdorf' (Federal Village). [1]
So what if Frankfurt was chosen as the capital of West Germany instead?