The first rails for horse-drawn tramways and gravity-powered railroads were simple wooden stringers. Later, wrought-iron straps on top of the wood stringers, and then cast iron rails, gave greater durability. The predecessor of the modern "T"-section rails first appeared on the Camden & Amboy in 1830, about the same time as the John Bull and other early U.S. steam locomotives.
Rail is designated by its weight per yard. At the start of the 1900's, heavy main line roads used 100-pound rail, while industries and shortlines had rail as light as 40 pounds. The most common size in service on heavy main lines today is 136 pounds, though sections as large as 152 pounds were once used on the Pennsylvania Railroad. Rail may be laid in 39 foot lengths, or in welded "ribbons" thousands of feet long.