I have a copy of a Gridley family letter which was written about 1860-1862 by Celestia Gridley (in Illinois, daughter of Timothy Gridley Jr.) to her cousin, George W. Gridley son of Wallace Augustus Gridley in Oregon. In this letter she writes:
"It was Theresee Augusta Gridley that died.I had forgot her name until Father told me."
This is obviously too early to be you Augusta Gridley ... but, I thought there might be a connection.
Also, I am always trying to determine who the parents of Wallace Augustus Gridley might have been. Our family bible says he was born in 1816 in Vermont. Is there a fit with the Michigan Gridleys?