http://www.connecticutbarns.org/index.cgi/3923

ConnecticutBarns.org has a newspaper clipping advertising the teaching of square rule of framing dating to 1814. The newspaper clipping is near the bottom of the page. Local (New Haven county) timber framers believe they have evidence that a frame was constructed in 1795 or there abouts using the square rule.

Framing square collecting is popular with the barn historians at least from what I've seen. One scenario is the local blacksmith made the framing square(s) to the local barn builder's specs. Bringing square rule to the area via the layout tool.

Neat stuff.