At one point in episode 26, one minor character complains how he has lost money on, amongst other things, his investment in a railway. This was set in 1799, some 27 years or so BEFORE the world's first railway was constructed.
The slang term of "sawbones" is used for a doctor throughout the series, even though it was unknown and not used until the late 1820's, some 20 to 30 years after the series was set.