Paul:
 
A few years ago my company conducted a partial excavation of a deck-style
turntable in Folsom, California.  It was the first turntable installed west of
the Mississippi and dates to 1856.  We found the pivot stone, brick reinforced
pit, inspection trench, ring rail and a second wall from a later 1866 A-frame
turntable.  Not the east coast, but still railroad.  For more information
contact me off list at
 
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Mary Maniery