Sarah Kliff at Ezra Klein's blog provides data from the New England Journal of Medicine on what we die of. (Around 1812 some of us exploded.) There's a chart summarizing the differences between 1900 (my parents were alive) and 2010 (I'm alive). I'm copying the graph:
I think the declines in many causes are attributable in part to "nanny" government, that government which ensures people, particularly in urban areas, have clean water and good sanitation, which oversees inoculations for things like diptheria and flu, which fights TB (which my mother had), (I understand some will argue against government intrusion. I remember when I got my TB vaccination in school, then my arm started to get swollen and painful. It was then I learned about mom's TB, which meant that my body reacted to the shot. There are gains to government intrusion, as there are costs, but I'm more impressed by the gains, at least in the field of public health.)
You really ought to read the Journal article in its entirety. Who knew that in 1912 they were worried about sedentary life caused by the automobile, or boasting of the superiority of Americans at the Olympics because of the diversity of our races? It's fascinating how other strands of our history appear in the annals of medicine.