Khlong Thanon Trong (Thai: คลองถนนตรง) was a khlong (canal) and a parallel road built by King Mongkut around 1857. Later, different sections of the canal became known as Khlong Toei and Khlong Hua Lamphong. "Khlong Toei" means 'the canal of pandan', as the plant grew along the southern bank of the canal. The road was renamed Rama IV Road by King Vajiravudh in 1919. In 1947, a large portion of Khlong Toei canal was filled to expand the Rama IV Road surface.