Just look up history (or what have you) and set the date to 19th century, or before 1920, or whatever range you like. There's a tab at the top right to download as PDF for free.
I recommend George Botsford's history books among others.
Also check Librivox.org for tons of public domain audio books for free!
Where can I find these books? I'd love to raise my kids with them
https://books.google.com/
Just look up history (or what have you) and set the date to 19th century, or before 1920, or whatever range you like. There's a tab at the top right to download as PDF for free.
I recommend George Botsford's history books among others.
Also check Librivox.org for tons of public domain audio books for free!