Forgive me if this has been posted before, but I found
this amazing chart detailing the leading causes of death between 1900 and 1998. It’s organized by year and sex, and very helpful if you want to know common causes of death for a specific year. It is limited to the United States, but quite extensive.
It certainly helped me a lot when I was trying to figure out what my character's parents could have died of in 1924. I hope it helps others!