CommonLit has a large (and constantly growing) library of reading materials. For example, I had my students read a piece on the Civil Rights Act of 1964 published by the National Park Service, pieces on sit-ins and Black Power from UShistory.org, and a piece called "Perspectives on Violence" that compared Bible passages about violence to the views of MLK and Malcolm X.
I was able to assign all this reading because CommonLit makes it easy. You can create classes and assign the reading to each class. Each passage comes with guiding questions, comprehension questions, and discussion questions. The comprehension questions are automatically graded. I used the discussion questions for a follow-up writing assignment. The site also allows you to track student progress in reading and writing skills.
The site's not perfect--there were a few glitches--but it's a great resource to supplement most lessons, especially for English teachers looking for non-fiction to pair with fiction. I'm looking forward to using it more. And best of all, it's FREE.