Marvel Studios head Kevin Feige confirms Chris Evans wasn’t originally on Marvel’s list for Captain America, though once the role was offered to Evans, he turned it down twice.
A cover story from The Hollywood Reporter revealed that Marvel began searching for its Captain America in early 2010 (Captain America: The First Avenger began shooting that June after Evans was cast in March), though Evans wasn’t on the initial list. Marvel was “determined to cast an American as Cap,” but Evans wasn’t being considered mostly because he had played the Human Torch in two pre-MCU Fantastic Four films.
Source: IGN.com Marvel Boss Says Chris Evans Wasn't on Original Captain America List