Sorry I forgot the ?.....The raw string was widely used across the NA Range. Some were twisted, some not, and some made from sinew, or reptile hide or groundhog hide, Some made from split cane.....I have to assume that every region had it's preferred string material and method.
Some of the Eastern bows had single strand strings some twisted some plain. Any bow that is near to 50# I make a 2 ply 3/8 twisted string. Probably overkill but that size made me all warm and fuzzy. Speaking of strings another really good material is some animal gut (intestines) I have heard that racoon gut was quite common in the Eastern and Mid Western areas.
Also keep in mind that twisting (that is not overdone) and then drying makes a dense and strong cord. Meaning the diameter when finished is a lot smaller than when it was stretched out wet.
rich