Dagny Taggart and Hank Rearden
We really have co-protagonists in this book, though Dagny is arguably the chief protagonist. We follow their stories from the very beginning. They are the two last holdouts in Galt's strike, so we follow their journey as they gradually decide to join the strike. We root for these two characters, we get the bulk of the book from their perspectives, and for a long time they are the only two "heroes" in the entire novel.