Minnesota Digital Library (MDL)
MDL is a statewide collaborative effort between libraries, archives, historical societies, and museums to create a digital collection unique to the state of Minnesota and its residents.
Try their searchable database, Minnesota Reflections, to access more than 6,000 images of Minnesota history.
Also, check out MDL's Resources for Educators. These are free resources designed to illustrate and explain how digital resources can be integrated into the classroom curriculum.