I’ll start with an easy one.
Who was the first president to ask congress to declare war?
Is cheating allowed? Can we Google?
Seeing as how no one has answered you, I’ll cheat.
Madison, War of 1812.
This was also the first time Congress, asserting their Constitutional duty, declared war.
Wait a minute! Do I win anything? 
How many presidents were there under the Articles of Confederation, what were their names, and what were the dates of their terms?
What was the first colonial government, in the land that became the USA, that declared the separation of church and state?
Here’s one that I don’t know the answer to, but I’ve always wondered:
Who was the most recent US President NOT to be a millionaire on taking office? My guess would be Eisenhower, but if that’s wrong I think you’d have to go a long long way back …
I was under the impression that Clinton was not a millionaire.
And I’m pretty sure Truman was not a rich man.