Your cottonwood is a loose term that can mean any one of a number of different types of poplar including the black poplar but not the Italian poplar, possibly the Canadian poplar but probably not the version of the crossing of the black poplar and Canadian poplar that is the most widely planted poplar here in the Netherlands making it the most likely candidate for the wood I was using for the shingles. To complicate matters more, tulpinhout, which could be translated literally into tulip wood, was the wood, (do you see a Dutch connection there?) we used for our very first project back at the woodworking school and they said the Americans called it yellow poplar, but it is really magnolia, but does bare striking resemblance's - the wood, that is not the tree - to poplar wood, but what you have written strikes me as familiar because where I come from we only had cottonwood and aspen as well.

Greetings,

Don Wagstaff