Has anybody got any idea when beaverboard began being manufactured, and when its production stopped? 

According to 20th Century Building Materials, edited Tom Jester, "Beaver Board" was a proprietary name of fiberboard manufactured by Beaver Board Company of Beaver Falls and later Buffalo, NY. Between 1913 and 1920, the company was awarded a 6 patents on its pulp-composite wallboard, although some Buffalo city directories seem to indicate that they may have been producing it as early as 1907.

 

Fiberboard was produced as early as 1772. The first US patent was issued in 1858. Jester's book notes that it was probably not mass produced or readily available until the 1910s.

 

Julip the Silent (until Prodded)