T rail

Iron-strapped wooden rails were used on all American railways until 1831. Col. Robert L. Stevens, the President of the Camden and Amboy Railroad, conceived the idea that an all-iron rail would be better suited for building a railroad. He sailed to England which was the only place where his flanged T rail (also called T-section) could be rolled. Railways in England had been using rolled rail of other cross-sections which the ironmasters had produced.
See more at Wikipedia.org...

See under T.