Phra Phuttha Yodfa Bridge, widely known as the Memorial Bridge, is a landmark of Bangkok and a major engineering achievement of the early 20th century. The bridge was commissioned by King Prajadhipok (Rama VII) to mark the 150th anniversary of the founding of Bangkok and to honour King Rama I (Phra Phuttha Yodfa Chulalok), the founder of the city. The king envisioned a project that would include both a royal equestrian statue and a bridge connecting the old capital of Phra Nakhon on the east bank of the Chao Phraya River with the growing district of Thonburi on the west bank. This new bridge would improve transport and communication and encourage the expansion of the city across the river. Prince Kamphaengphet Akkarayothin was appointed as the director of construction, overseeing the realisation of the king’s vision.

Work began in 1928, and the bridge was officially completed and opened in 1931. The construction contract was awarded to Messrs Dorman Long & Co. Ltd., a renowned steel construction company based in Middlesbrough, England. Established in 1875 by Arthur Dorman and Albert de Laude Long, the company was internationally recognised for iconic projects such as the Tyne Bridge (1928, UK), the Omdurman Bridge (1926, Sudan), the Tees Newport Bridge (1934, UK) and the Sydney Harbour Bridge (1932, Australia). The involvement of Dorman Long highlighted the cosmopolitan and modern ambitions of Siam during this period.

The Memorial Bridge is a steel truss bridge with a central lifting section. It measures 229.76 metres in length, 16.68 metres in width, and its deck rises 7.5 metres above the river. The middle section can be lifted using electric or steam-powered engines to open a 60-metre-wide passage, allowing large ships to pass along the Chao Phraya. This engineering solution reflects the influence of Industrial Revolution technologies that had transformed transport systems around the world. The design drew inspiration from notable bascule bridges such as London’s Tower Bridge (1894) and Broadway Bridge in Oregon (1913).

The King Rama VII entrusted Prince Narisara Nuvadtivongs with the design of the bridge’s site plan. He conceived the bridge’s site plan in the symbolic form of an arrow: its head pointing towards Thonburi and its tail anchored on the Phra Nakhon side, where the Rama I Monument was placed. The arrow motif carried special significance, as King Prajadhipok’s personal emblem, derived from his name “Prajadhipok Sakdidej,” was an arrow (“dej” meaning arrow). Thus, the plan embodied both the celebration of Bangkok’s history and the personal royal identity of its reigning monarch.

The total cost of construction was 4 million baht, an enormous figure during the economic depression that followed the First World War. King Prajadhipok personally donated 2 million baht from his own funds, with the rest covered by the government and contributions from the people.

Since its inauguration, the Memorial Bridge has stood as a monument to King Rama I, a symbol of Bangkok’s growth, and a mark of Siam’s openness to modern technology. It facilitated the physical expansion of the city into Thonburi, strengthened economic activity on both banks, and demonstrated how global engineering expertise was adopted locally. It remains one of the city’s most historically significant bridges and a tangible reminder of the transition of Bangkok into a modern capital in the early 20th century.