Particle Accelerators

[TSands2000]

And just to bring up a topic *other* than current world events, how about 
this:

If anyone is informed and interested, I have been thinking lately about 
particle accelerators.  I know they are built to provide an infrastructure 
for various experiments in quantum physics, but beyond a basic understanding 
of subatomic phenomenon my knowledge on their true purpose is limited.  How 
many are there in the U.S.?  Where are they located?
 
Just wondering ...

T.Sands