The church was built in middle of the 13th century, the tower was added in 1450. The tilt of the tower is thought to arise from a combination of its oak wood foundation and wet soil.
However, as Craig Whitlock from the Washington Post reports, this caught by surprise the inhabitants of Bad Frankenhausen, whose "Church of Our Beloved Ladies by the Mountain" is tilded only by 4.4° but is twice as high. So the locals want their church to be acknowledge as the "World's Crookedest Tower".
Germany, the land of crooked and tilted towers ;-)