A few more details, from digging through the french wiki (has a lot more info than the english one)
2057, 9 August: Big D's death (or 'death'?), creating the rift
2061, 24th of December: Ghostwalker's astral form comes flying out of the rift, surrounded by a haze of spirits -- including the shedim (to appear in notable numbers, at least) (shortly after he appeared in physical form in Denver). This is probably covered in The Year of the Comet
2073, 18 July: Ghostwalker leads a ritual, including Harlequin, Hestaby, Erhan, Frosty, Lugh Surehand, Jonathon Reed, Aden, Aina Dupree an unknown, and some very powerful artifacts whose combined presence was stressing reality. (Artifacts Unbound). About 600 civilians were killed, 2000 wounded, and 3000 disappeared (presumed pulled into the rift). Aina Dupree was doing magic to protect everyone involved, but exhausted her magic and died. (Source appears to be Conspiracy Theories). President Colloton announced that several government agencies had worked together to close the rift.
A bunker was built around the rift at some point, but I couldn't find when. The ritual in 2073 caused extensive damage to the bunker.