A homemade bomb went off over the weekend in the Chelsea neighborhood of Manhattan, injuring 29 people, and a second was found nearby. Meanwhile five pipe bombs were found near a train station in Elizabeth, N.J. The FBI has identified a suspect and a search is under way.

If this seems particularly troubling, it might be useful to put the weekend’s effects in some historical context. I will try to write a longer post about this later today, but here’s a tiny little slice.

In 1970 alone there were 54 terrorist bombings in New York City. Three of those occurred on successive days from Sept. 24-26. March saw 10 separate terrorist attacks in New York City. (Data comes from the Global Terrorism Database at the University of Maryland).

In short, and as with most things terrorism-related, we’ve been there before.

And now on to this week’s history:

• Sept. 18, 1997 — Egypt: Bomb attack on Cairo tourist bus kills nine Germans. Muslim militants are blamed.
• Sept. 20, 1984 — Lebanon: Islamic Jihad Organization detonates a truck bomb at the US Embassy annex in Beirut, killing 23.
• Sept. 21, 2013 — Kenya: Al-Shabaab gunmen kill more than 70 and wound 200 in an attack on the Westgate mall in Nairobi.
• Sept. 23, 2010 — Colombia: FARC military commander Victor Julio Suarez Rojas is killed in a Colombian military operation in Meta Department.
• Sept. 24, 2002 — India: Attack on a Hindu temple kills 31. Lashkar-e-Taiba is suspected of responsibility.