Primary evidence suggests recipes for chicken pot pie (in concept, but not name) were known in England as far back as the Middle Ages. As one would expect, these early meat pies were quite different from ones we know today. Robert May's Accomplist Cook [1685] lists several recipes for poultry pies (chicken, turkey, pheasant etc.). These generally still relied on Medieval flavors: pepper, salt, nutmeg, orange juice, lemon, chestnuts, mace, sugar, gooseberries, barberries, grapes etc. Vegetables were sometimes employed:
" artichock bottoms, or the tops of boild sparagus...Otherways for the liquoring or garnishing of these Pies, for variety you may put in them boil'd skirrets, bottom of artichokes boil'd, or boil'd cabbidge lettice...whole onions being baked...Or bake them with candied lettice stalks, potatoes..."
---The Accomplisht Cook, Robert May, facsimile 1685 edition [Prospect Books:Devon] 2000 (p. 212-3)
The oldest American recipes we have specifically titled "pot pie" are from 1839
From this website.http://www.foodtimeline.org/foodpies.html