We still have not found a marriage record, however we did find an exact date listed in the 1927 Dartmouth College records which provide updates of the life of the 1917 graduates of Dartmouth College.
This update shows Bartlett Chauncy Shackford's nickname was "Bart", that in 1927 he was the proprietor of the Long Beach Diagnostic Laboratory in Long Beach, California, that he lived at 4241 Vista Street in Long Beach, and that he was married August 5th, 1919 in Roslindale, Massachusetts to Rose Wincester Karnan.
We'll keep looking for a marriage record but until then will presume that the information provided to Dartmouth College for their ten year update was correct. We'll also see if we can find other information about their marriage in newspapers.
We don't know for sure how they Bartlett and Rose met but assume that the connection may have been from Rose's older brother Robert Parker Karnan who was in the same college class as Bartlett.
"Massachusetts, Marriage Index, 1901-1955 and 1966-1970," images of the Massachusetts Marriage Index, Ancestry.com (http://www.ancestry.com : accessed 4 November 2015), Bartlett C Shackford
Sanborn Ralph, Nineteen Seventeen Dartmouth College (Hanover, New Hampshire: 1927), page 239; digital images, Ancestry.com (http://www.ancestry.com : accessed 4 November 2015