Hi Ken,
Yes, square rule was applying the techniques of early mass production to timber framing. The roots of this came from Europe in the late eighteenth century and then found fertile ground to flourish in the States from the beginning of the nineteenth, initially in military applications then on to agricultural and consumer goods. Division of labour, standardization, interchangeability, and mechanical power sources enabled the States to supply the demands required of it and to utilise its specific human and material resources in a way that Europe was not able to initially.
So further information on these early square rule frame would be very interesting.
I know Eli Whitney( who was a central player in the production of the smithfield rifle) had a square rule barn built in 1816 at his farm. But I bet he was not the first.