Here are a few of the things I've researched for the 1950's alt-history setting I'm working on
What can make guns misfire?
History of women's suffrage
History of the American Civil Rights Movement
Do nuclear weapons work in space?
Largest practical nuclear weapon
Timelines of both world wars, broken down by month & year
Who lost the American presidential elections 1920-1932
The Laws of Thermodynamics
Who was the Roman equivalent of Hecate?
Aramaic, Sami, Yoruba, and Shawnee names
Martial arts traditions of India