Hi Phil, I couldn't view your attachment, but you are one of the most savvy history folks I know.
That being said, these are my ideas. Go to or phone the Town of Somers Clerk and ask about Land Records and maps of early property owners. Back in the day when Westchester was rural,
local civil maps indicated land tracts with owners names on them. 2nd I know that property had to be registered on the county level. If you find out that the county archives has anything, get back to me and I'll retrieve it for you. They charge $2./ per page to scan from huge ledgers, and that machine must be working to get such items.

Circa 1965 a Dennis FLOOD lived in that area and graduated from then St. Mary's HS in Katonah.