Oh thanks for the 1855 state listing...I couldn't find it! They were on the 1860 census but not on the 1870 so I assumed she'd died. Don't know where he went.
Yes, that helps as lot that she was Nancy A(nn) as I am sure that she is the Ann in the death you list. She is listed on a headstone in Burial Hill as well as well. I had gone all through every death record from 1860 to 1872 (year of John's death) via American Ancestors database of Mass Vitals for Plymouth deaths and she was the only Cassady with a husband John. He died in 1872.
John S married Mary McGlinchey and I have letters of congrats from friends and rellies on their 50th wedding anniv in 1895. Their daughter, Margaret Anne married Edward A. Wright who was my great grandfather and a Mayflower descendant. So we have lots on the Wrights but nothing on Cassidys.
Thanks again for your persistence...most appreciated!