does anyone know a web site that will tell you the population of any country 100-150 years ago?

Answer 1

Atlases!!!!!! A history atlas can be a good source of info for demographics on any country and on different periods of time. Look up "history altas" or "atlas of world history" in a search engine and that should bring up something useful.

There's always wikipedia, and that can be a good source of info and external links for the country you are looking up.

100 to 150 years ago, there was a much lower world population than there is today, so, given the country, there may not be a lot to report.