Numerous horse-drawn tramroads were constructed in South Wales during the Industrial Revolution, chiefly between the years 1790 and 1830 and connected with the iron and coal-mining industries. The earliest tramroads were "edge-railways", where the wagons were guided by having flanged wheels running on plain rails, but from around 1800 most tramroads in the area were being made according to the principles of Benjamin Outram, with unflanged wheels running on L-section tracks fixed to stone-block sleepers; and many earlier lines were also rebuilt to these specifications. Track gauges were not standardised, but most were between 3 ft. 4 in and 4 ft. 4 in.