The 1921 viaduct has significance because, it is part of the Bowenfels to Wallerawang duplication, the last of such works dominated by brick arch construction, the curved viaducts, 1870 and 1921, are an impressive pair of structures on the outskirts of historic Bowenfels, the duplication work contributed significantly to the railway extension to Bathurst and to the continued development of Western New South Wales, for land transport to Sydney and with six 12 meters clear spans on tall brick piers, it is one of the largest brick arch structures on the New South Wales railways system.