Grades One through Six at my homeschool library blog. These have come in handy for extra study work. I don't print out the entire book, just excerpts which I edit, save, publish(optional) and print with Google Documents.
I found a few short stories with comprehension questions that fit nicely with a fourth grade reader story about Benjamin Franklin. I'll share these soon. I found the short stories in books by searching my homeschool library's Elementary School Social Studies label. I've been adding, and adding to it, and am just now finding the library useful.
The vintage readers are worth a look, and convenient if you need something short and well written. Ds wanted to see a picture of Benjamin Franklin on his story page, so I pieced together something for him. We'll eventually borrow a biography at the library, but this was a good introduction which sparked further conversation with ds, who is still a young child.
If you are looking for a high moral tone, these vintage readers fit the bill. They are wonderful for teaching Christian values. Almost every story teaches a moral, especially in the lower grades.