I have a few suggestions. All qualify as historical fiction, appropriate for 7th grade, lots of research avenues, inventive characterization.
Kent State--Deborah Wiles. (And it's in verse!!!!)
We Dream of Space--Erin Entrada Kelly (Challenger disaster)
Walls--L.M. Elliott (Berlin Wall)
Amber and Clay--Schlitz (Ancient Greece)
Cuba in My Pocket--Cuevas (Operation Pedro Pan--pair with Margarita Engle)
Cathy Andronik
Presenter, Bureau of Education & Research
Retired, Brien McMahon HS, Norwalk