May 31, 1889: A poorly maintained dam on a lake bordered by affluent summer homes gives way in heavy rains. Fourteen miles downstream, a wall of water slams into Johnstown, Pa. The Johnstown Flood kills an estimated 2,200 people.
May 31, 1935: An earthquake takes 15,000 lives in Quetta — then part of British-controlled India, and now a part of Pakistan.
May 31, 1970: An 8.0 magnitude earthquake off the coast of central Peru claims 66,000 lives. Nearly half the deaths are the result of a massive avalanche triggered by the quake. The north side of Mount Huascarán collapses (at right), burying two towns in a massive slide of ice, snow and rock.