In five games playing the Philidor Counter Gambit as Black, Paul Morphy never lost, winning three and drawing two. I have often wondered what line Morphy would have chosen as White against the PCG, guessing that he probably would have developed a piece by either 4.Bc4 or 4.Nc3.
Actually there is game where Morphy favored 4.Bc4 over 4.Nc3, but there was little choice because he was playing at queen knight odds! The opening moves were 1.e4 e5 2.Nf3 d6 3.d4 f5 4.Bc4 fxe4 5.Nxe5, resulting in a drawn rook-and-two-pawns versus two bishops endgame.
There is an error in the score of the game. Black played 34...Bb2, not 34...Bg7.