The Minnesota Literacy Council has developed quite a few excellent online reading comprehension exercises (for intermediate and advanced English Language Learners) related to United States History.
I’ve placed links to them in the appropriate sections of my Geography and United States History page.
You’ll find the Early America quizzes under the Building a New Country section. A New Country exercises are in the A New Country Grows category. A New Century tests are under The Nation Grows and Divides.
These exercises, along with quite a few others you’ll find by following links on my site, were created using Hot Potatoes, a popular and simple software program that can be downloaded for free and used by teachers. You can find tutorials on how to use Hot Potatoes on my Teacher’s Page under Create Tests and Exercises.