Because you wondered if the 3-iron-hooks eagle breastplate you found could have seen service in the civil war or was just used by an earlier soldier, I did some additional research for you.
I super-magnified your photo of your breastplate's front, to try to find an EXACT match for it among the many variations of Model-1826 breastplates shown in the "American Military Belt Plates" book. After a lot of close squint-eyed examination, I succeeded. Your plate's exact match is shown in that book as plate #446, on page 282. The book says that particular version was made from 1836 to 1841, probably at the Allegheny Arsenal, and some have been found on civil war battlefields.
That information indicates it's at least possible that the one you found saw service in the civil war, rather than merely worn by an earlier (1840s-50s) soldier. You said you found it at an old house-site foundation in Kentucky. If there was any civil war activity at that house-site, there ought to be at least one or two 1861-1865 military relics there ...such as a civil war uniform button or a Minie-bullet. If you don't find any military relics there from that specific time-period, you've got the most-likely answer to your question.