The Big Trail was simultaneously shot in both 35mm and 70mm (Grandeur) versions. The Big Trail is the only one of three Fox Grandeur films which has survived in its original wide screen format. The other two are Fox Movietone Follies of 1929, completely lost, and Happy Days, which survives only in standard format. Did you know that five different versions of this film were shot simultaneously. (1) a 70mm version in the Grandeur process for exhibition in the biggest movie palaces; (2) a standard 35mm version for general release; (3) a 35mm alternate French language version La piste des géants (1931) (4) a 35 mm alternate Spanish language version La gran jornada (1931), and (5) a 35 mm alternate German language version Die große Fahrt (1931). The three alternate language versions were shot with (mostly) different casts. So the answer to your question is True! I cheated on this one and did some research (hope that counts)! :)
At least, I admitted to it! :)