I just did a quick scan of the book (online PDF) and I'm of the opinion that it's impossible to know for certain. I think we can know the sequence of the first and the last, but not most in the middle, because that information is never stated in the book.
The First:
1. John Galt
2. Ragnar, Francisco (maybe Hugh?)
3. Midas Mulligan
The Last (in reverse order):
1. Dagny
2. Hank
(And here my memory gets murky, but perhaps the Utah guy and Dannager)
But for those in the middle, the timeline is very murky.