The American, colonial government established it in 1901 as the Philippine Weather Bureau, which expanded into meteorology, astronomy, and geomagnetism. The work of the bureau was interrupted by the Second World War. During the Battle of Manila, all of the instruments and important documents of the bureau were destroyed and it ceased to function. A specific government agency was established in its place. The observatory resumed operation in 1951 in Baguio, mainly for studies on seismology and the ionosphere. In 1963 it was transferred to the Loyola Heights campus of the Ateneo de Manila University where it continues its studies into seismology, geomagnetism, and radio physics, among other areas of research.