The Hiroshima Post Office was established in 1871 as the core of communications in Hiroshima. It was rebuilt in 1893 as a three-story (plus underground level) modern brick building with a mortar-covered section. It's reputation is apparent in the common phrase of the day, "Number 1, Prefecture Office, number 2, the Post Office". Facing a three-way intersection, it stood next to the spot where a parking tower is located today. Across the street from the parking tower is the Shima Hospital hypocenter plaque. A clock tower stood in the three-story entrance of the post office. Because it was at the hypocenter, it was exposed briefly to heat of 3,000-4,000 degrees centigrade and was dealt a shock of around 30 tons per square meter. The building crumbled immediately. Those inside undoubtedly died without seeing the flash or feeling the blast. By evening that day, unidentifiable white bones and charred corpses lay strewn among the rubble.
At the time, many male employees had been drafted and were consequently in other places. Most of those killed by the bombing were women hired to fill the vacancies, mobilized girl students, and girls from national school upper levels.
On the monument is written: "Monument built for those who died on duty. 288 officers of the Hiroshima Post Office killed in the atomic bombing." However, a newspaper company study in 2000 revealed that eight children and one girl student who were in the day-care room were also killed.