Saying everyone before Darwin was a creationist is like saying everyone before Martin Luther was a Catholic.
There were some pre-Darwinian evolutionists, and there were some scientists who were non-pious, irreligious or secular, but it just happens that neither of those states characterize any of the principle figures behind the early development of modern geology and the defining of the major geologic systems. They were observant Christians and creationists to a man.