Spanning the border between Scotland and England, which at this point follows the River Tweed, the Union Suspension Bridge (also known as the Union Chain Bridge) is located 5 miles (8 km) upstream from Berwick-upon-Tweed, close to Paxton House (Berwickshire) and the village of Horncliffe (in England). It is remarkable for being the world's oldest surviving carriage suspension bridge still open to vehicular traffic, and those standing on the bridge today marvel when they feel its oscillation as a vehicle crosses. Until the completion of Thomas Telford's great Menai Bridge linking Anglesey to the Welsh mainland over the Menai Strait (1826), the Union Bridge was the world's largest span wrought-iron suspension bridge to carry vehicles.
The builder was Captain Samuel Brown R.N. (1776 - 1852), a chain manufacturer who had, in 1817, patented his invention of the wrought iron bar-link chain, which was to be used in the construction of this bridge . He worked in association with John Rennie (1761 - 1821), who acted as consultant engineer and made suggestions to ensure its durability. The foundation stone was laid by William Molle in 1819 and the bridge, remarkably, took only a year to build.
The Union Bridge is 133.2m (437 feet) in length between the suspension points, 5.5m (18 feet) wide and is a Scheduled Ancient Monument. A plaque set into the wall, at the English end, commemorates its building. The opening ceremony on the 26th July 1820 was performed by Alexander, 10th Earl of Home (1769 - 1841), Lord Lieutenant of Berwickshire, and Sir John Marjoribanks of Lees (1763 - 1833), the local Member of Parliament. It was attended by another eminent Scottish civil engineer, Robert Stevenson (1772 - 1850) who produced a noted profile of the bridge in his Description of Suspension Bridges (1821). The artist and engraver, William Home Lizars (1788 - 1859) working with Stevenson, produced an engraved aquatint showing the first carts crossing the new bridge, which is now held by the National Library of Scotland.