I used to live in Western Nebraska about 10-15 years ago. I can pretty much confirm what Kota is saying about the Cheyenne area. Although that missile field streches out alot farther than you think because I used to drive past one silo when I was headed south on Nebraska 71 to catch I-80 to go Cheyenne. By looking at this map I see there were a few I didn't notice.
source:
http://nukewatch.com/weapons/index.html
So I'm not so sure, that they could catch all the silos with nukes if they wanted to. My guess is they were nuking Warren to disrupt the the command, control and support for those silos. I'm curious has anybody tried to figure out what the blast radius is from that nuke going off? I mean would it totally destroy Cheyenne or would there still be some buildings standing?