[ Ref. 170406 MMD, History of U.S. Standard Pitch, A = 440 Hz

The US adopted a foreign pitch standard: International Concert Pitch.

http://webstore.ansi.org/RecordDetail.aspx?sku=DIN+1317-1%3A1957 
  DIN 1317-1:1957
  Standard Tuning; Standard Musical Pitch (FOREIGN STANDARD)

https://www.iso.org/standard/3601.html 
  ISO 16:1975
  Acoustics -- Standard tuning frequency (Standard musical pitch)

See further History of Musical Pitch:

https://books.google.com/books?id=5UM0AQAAMAAJ&pg=PA27&lpg=PA27&dq=french+diapason+normal&source=bl&ots=aZDni8OPls&sig=HJotLLGbAeQ7W0w1oQBzkoAJr7U&hl=en&sa=X&ved=0ahUKEwj3wqe72JPTAhXmhlQKHZ5oBEsQ6AEIcjAS#v=onepage&q=french%20diapason%20normal&f=false 

https://books.google.com/books?id=olFHAQAAMAAJ&pg=PA864&lpg=PA864&dq=french+diapason+normal&source=bl&ots=XkKgo-TI-h&sig=aaGM1Q9cuOdFylbEnP2ZlmvgjaQ&hl=en&sa=X&ved=0ahUKEwiwyI2o2ZPTAhVHxVQKHfDWB204ChDoAQg0MAc#v=onepage&q=french%20diapason%20normal&f=false 

Respectfully,

Grant Chapman
West Point, NY