Actually, the boiler pressure on those early coal lift systems was more like
10psi. That was why the cyulinders were so large on the engines. Today,
we'd consider such a pressure to be basically worthless but back then, even
that little pressure was a great improvement over using horses to do the
lifting.
They also never thought of superheating the steam to gain additonal work out
of the steam but that is another thing.

--
Why do penguins walk so far to get to their nesting grounds?