However, it was not until the 20th century that there was national legislation on historic preservation. In 1961 the "Monumentenwet" (“Monuments Act”) was passed. It defined that any physical building or space that was at least fifty years old and “which are of general interest because of their beauty, their meaning to science or their social value” and must thus be preserved. In 1988 this Act was replaced by the "Monumentenwet 1988" (“Monuments Act 1988”) and in 2015 by the "Erfgoedwet" (“Heritage Law”).