ward histories.

As a stake historian, do i have to make a cover sheet for each ward in stake or just the Stake cover sheet?

I think that is a decision for you or your Stake President. I have seen both scenarios (where the stake lets the ward make their own cover sheet and where the stake tells the wards to use the stake one). I don't think any method is prescribed by the church. For the last few I submitted (a few years ago), we were instructed that a cover sheet was not needed from the ward.