From: Andreas, A.T. History of Chicago from the earliest period to the present time, Vol. I. Chicago: A.T. Andreas, 1884, pgs. 97-99:

Mrs. Juliette A. Kinzie died September 15 1870, at Amagansett L.S. Her death was caused by the fatal mistake of a druggist, who sent her morphine, which she unfortunately swallowed instead of quinine, which she had ordered.

Juliette was the author of: "Narrative of the massacre at Chicago: Saturday August 15, 1812, and of some preceding events." Fergus Printing Company, 1914.