Minnesota Native Bees is a free digital native bee field guide recently launched by Heather Holm. This is from the Facebook page:
We are a non-profit organization providing a free digital field guide illustrating the native bees of Minnesota and surrounding regions.
Check out the guide! https://www.beesmn.org
Our mission is to raise awareness about the importance of native bees, their diversity, natural history, and conservation. The intent of the online guide is to inspire research and participatory science, and cultivate a deeper awareness and understanding of native bees, resulting in their appreciation, conservation, and stewardship of their habitat.
Credit for photo of Common Eastern Bumble Bee: Ryan Hodnett, Creative Commons Attribution-Share Alike 4.0