 While Whitton's stone arch viaducts were replaced by brick bridges during duplication works in the 1920s, many of the original stone bridges remain extant, including the Middle River Bridge at Marrangaroo.The stone viaduct was replaced in 1923, following duplication of the track and construction of a replacement brick and masonry viaduct, comprising four spans.Marrangaroo railway viaduct was listed on the New South Wales State Heritage Register on 2 April 1999.