Jim,
 
This is a long way from NY, so if you're interested only in New Yorker's  
usage of the maps, this will not apply.
 
However, the Silver City, Owyhee County, Idaho Sanborn map, was  utilized by 
the Bureau of Land Management in Boise, Idaho, and by the Idaho  State 
Historical Society.  The map was used extensively as a guide to  help identify the 
location of past buildings in Silver City, which in the 1860s  became a gold and 
silver mining town of significance in the Owyhee  Mountains.  Over the years 
as mining dissipated, so also the population,  and buildings disappeared.  
Today it is but a shell of it's original  existence, but still contains a few of 
the old buildings and residences,  maintained by descendants and interested 
individuals, and is designated an  historic district of the State of Idaho.
 
The map (re-drawing of), was published in the "Silver City Environmental  
Impact Statement," published by the BLM, (I believe in the 1970s) and has  been 
used as a souce of reference by Idaho historians ever since.
 
If this is of interest to you, you could probably contact either the Boise  
BLM office or the ISHS for their evaluation of its worth.  
 
Liz