The Roswell (Corona) crash is well know and documented. It is universally accepted that the crash took place in early July (or late June) of 1947.
http://en.wikipedia.org/wiki/Roswell_UFO_incident
The Army Air Corps made a press release on the 8th of July, 1947 concerning the crash.
Historically, 1947 is a very interesting year:
The National Security Act of 1947 (an act of Congress) was signed into law on 26th of July, 1947.
http://en.wikipedia.org/wiki/Nationa...ty_Act_of_1947
The Army Air Corps became a separate entity (the U.S. Air Force) on 18th of September 1947.
http://en.wikipedia.org/wiki/United_States_Air_Force
The remnants of the OSS basically became the Central Intelligence Agency on 18th of September 1947.
http://en.wikipedia.org/wiki/Cia
1947 was a very interesting year indeed.
M