Jack -
Presuming this identification as "Whitworth guns" is valid, that would suggest at least four in the west; but I'm still grappling with your new find. For now, I believe it would be a leap to further presume these were breech-loaders. The Whitworth was one of the most mis-identified pieces of artillery, so I always start by being skeptical. Yes, I'd love to see the Pointe Coupee inventory.
John