The rapid sand filter or rapid gravity filter is a type of filter used in water purification and is commonly used in municipal drinking water facilities as part of a multiple-stage treatment system. The first modern rapid sand filtration plant was designed and built by George W. Fuller in Little Falls, New Jersey. Fuller's filtration plant went into operation in 1920 and its success was responsible for the change to this technology in the U.S. Rapid sand filters were widely used in large municipal water systems by the 1920s, because they required smaller land areas compared to slow sand filters.