Tradition Online has posted R. Shnayer Leiman's classic article "The Adventure of the Maharal of Prague in London: R. Yudl Rosenberg and the Golem of Prague" (link). The key paragraph is on pages 32-33:
Did the Maharal create a Golem? If our only evidence for the Maharal’s Golem came from the writings of R. Yudl, we would perforce conclude that the Maharal’s Golem is imaginary. In fact, the tradition that the Maharal created a Golem antedates R. Yudl. Already in 1837 (before R. Yudl was born), legends about the Maharal and the Golem appeared in print. The early printed accounts indicate that these legends had an oral history before being recorded. They probably go back at least to the second half of the eighteenth century. Unlike R. Yudl’s version, these accounts never speak about blood libel, and they know nothing about a Cardinal Johann Sylvester. Nonetheless, the gap between the death of the Maharal in 1609 and the first printed account in 1837 is striking. There is certainly no evidence contemporary with the Maharal that he—the Maharal—created a Golem. Rationalists dismiss the late accounts out of hand; mystics hold on to them dearly, though they often seem unaware of just how late and thin these traditions really are.