I am after information on these woodworking tools the belt sander and router.

If you have any information about when these were first invented and what they replaced in terms of manual tools. I would appreciate any information that you would have.

Well, in my phd treatise, I conclusively proved that the belt sander replaced the hand sander.

And that the electric router replaced the hand router, but quickly also replaced moulding planes, scratch beaders, and recently, hand carving.

But only in places where they had electricity. The relatively high cost of the "new" power tools led to tsome very peculiar union rules.

But in all seriousness, The Carpenters and Jointers have a history project, I think run out of a NJ or NY local that deals with this subject. You may wanna do a search under "Carpenter's history project" and see what turns up. It might only be related to skil-saws

You might also wanna try a search on some of the patent data bases. There is a lot of interest in old handtools, but not much activity in old power tools