The Ghost Map: The Story of London's Most Terrifying Epidemic--and How It Changed Science, Cities, and the Modern World, by Steven Johnson is a very interesting book. The pump handle! This book has it all!
John Snow's data journalism: the cholera map that changed the world
The most famous map of cholera is that of John Snow (LL). There is nothing very special about this map, except that it helped display how people caught cholera. Another map then published detailed a similar relationship and added time and sequence to the scenario. Still, the best map was that of John Lea (center). Snow refuted it. But 25 years later we would learn that Lea was right.