N.Y. Railroad Law § 51

§ 51. Weight of rail. The rail used in the construction or the\nrelaying of the track of every railroad hereafter built or relaid in\nwhole or in part shall be of iron or steel, weighing not less than\ntwenty-five pounds to the lineal yard on narrow-gauge roads, and on all\nother roads not less than fifty-six pounds to the lineal yard on grades\nof one hundred and ten feet to the mile or under, and not less than\nseventy pounds to the lineal yard on grades of over one hundred and ten\nfeet to the mile, except for turnouts, sidings and switches.\n