Imminent Domiciles

Across the street from where I live is a block of nothing but houses.  Or was.  About a month ago, a fence was put up around the houses and since then they've all been knocked down. I have no idea what's going up, but I'm guessing apartments. (I probably got a notice in the mail from the city which I tossed.)

The houses were old, and nothing special, but they were decent and people lived in them.  So how did the city get the residents out?  What sort of notice did it send them?  How much did it have to pay?  Was there any help in finding a new place?  How tough would it have been to resist?  We're talking over twenty houses, with families that have been there for years.

I don't recall studying eminent domain in law school, but I imagine the state of California and the city of Los Angeles doesn't have too many limitations, and is pretty tough on just compensation.  Right now I'm trying to imagine what it feels like, if you're not planning on moving any time soon, to be told by the authorities to hit the road.