Allendale is Consolidated city-township in Ottawa County in the U.S. state of Michigan. It is also a census-designated place (CDP) for statistical purposes. The population was 17,579 at the 2010 census. The city-township is located within Allendale Charter Township and the CDP area consists of about the northern two thirds of the township, from the eastern boundary with the Grand River west along Pierce St., north along 75th Ave., then west along Lake Michigan Drive (M-45) to the western boundary of the township. Apart from the CDP definition, the city-township is centered at the intersection of M-45 and 68th Ave., which are the only roads which cross the Grand River in the county east of Grand Haven.