With a little help from Joseph Seinkiewicz at NOAA I discoverd that the record occured in 1977.
“The lowest non-hurricane barometric pressure reading from anywhere in the United States was a 27.35? (927 mb) reading at Dutch Harbor, Alaska on Oct. 25, 1977.”
http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1674