Battambang was established as an important trading city with around 2,500 residents in the 18th century. The population was centred along a single road parallel to the Sangkae River (Stung Sangkae). In 1795 Siam (modern-day Thailand) annexed much of north western Cambodia including the current provinces of Banteay Meanchey, Battambang, Oddar Meanchey, Pailin, and Siem Reap into the province of Inner Cambodia. This first attempt at modernization resulted in well-defined streets laid in a grid pattern, building of urban structures and three main streets parallel to the Sangkae River, and the linking of both banks by the construction of two bridges in 1917. attambang was acquired by Thailand in 1809 and returned to Cambodia in 1907.