Growing up in Los Angeles, I remember the last Friday 10:00 a.m. civil defense sirens going off. I always thought that if the Soviets were going to attack us, the last Friday at 10 o'clock would be the time to do it. Everyone would think it was a test.
The sirens have long been silent. The system no longer works. It was disconnected in 1985. However, most of the sirens still dot the landscape, monuments to the Cold War.