Guys,
Sandpaper was used from very early times, as far back as the 13th century. Modern sandpaper started to be mass produced in 1833 in England and 1834 in America. This sandpaper was actually called "glass paper" as the abrasive was crushed glass rather than sand. The process was patented in 1834 by Isaac Fisher, June 1834, patent number X8,244. Prior to this patent the manufacture and use of sandpaper was dependent on the artisan using the sandpaper. They made their own, but certainly the early glues and abrasives were such that the sandpaper was probably nowhere near the quality product available to us today. Research in the US patent records can often help us answer such questions. Check out datamp.org.
Jim