The entire avenue was built in the reign of King Rama V. It was the largest and widest avenue at that time. Ratchadamnoen means the royal passage, because it links between the Royal Grand Palace and Suan Dusit Palace.
There are three parts of Ratchadamnoen Avenue, the middle part is called Ratchadamnoen Klang or Central Avenue, and the outer part near Suan Dusit Palace in the north is called Ratchadamnoen Nok or Outer Avenue.
In the past, both sides of Ratchadamnoen Klang Avenue were lines of Mahogany Trees. These trees were taken away in 1941 when the huge post-war style buildings were constructed on both sides. All buildings along the avenue have the same material and style and most of them are used as government and private offices.