The UK supplies much of world's Rhubarb, most of it from the so called Rhubarb Triangle in Yorkshire https://en.m.wikipedia.org/wiki/Rhubarb_Triangle where it is "forced", it apparently grows so quick you can hear it!
Wikipedia says it was known simply as "pie plant" in the US in the 19th century.
Although strawberry-rhubarb pie is a common combination, I recall pies of my childhood being rhubarb alone.