In the very early morning at 03 h 53.7 m on 15 April 1909 (local time), a large earthquake occurred in northern Taiwan. In all, 9 persons were killed and 51 injured; 122 houses collapsed along with damage to another 1050 houses. This earthquake was one of the largest and most damaging events of the 20th century for the Taipei Metropolitan Area. The epicenter estimated by Hsu (1971) was determined to be 25¢XN, 121.53¢XE and its focal depth and earthquake magnitude evaluated by Gutenberg and Richter (1954) were ~80 km and MGR = 7.3, respectively. The event took place underneath the Taipei Metropolitan Area and might be located at the western edge of the subduction zone of the Philippine Sea plate. In this study, the magnitudes of the earthquakes determined by others will also be described.