Kenneth Regan's work on Intrinsic Performance Ratings includes estimated ratings for Morphy, which vary widely from event to event but average around 2300, whic

Kenneth Regan's work on Intrinsic Performance Ratings includes estimated ratings for Morphy, which vary widely from event to event but average around 2300, which I think matches the intuitive perception of his strength that modern strong players have. https://cse.buffalo.edu/~regan/papers/pdf/Reg12IPRs.pdf https://cse.buffalo.edu/~regan/papers/pdf/Reg12IPRs.pdf (Of course, as with all historical players, he would be stronger if he were re-animated today and exposed to modern principles and openings.)