During last night's live CNN broadcast, anchor Rosemary Church asked why police didn't use water cannons instead of tear gas, prompting a sidelong glance from her desk partner.

If one has no knowledge of water cannons' place in American civil rights history, it probably seemed like a reasonable question. But anyone who lived through or studied that era remembers Birmingham.

Here's a little history lesson for Ms. Church:

https://www.youtube.com/watch?v=o54n7HXwOhc