It has been there for a long time Offut and Omaha used to be the most targeted place on Earth.
Of course, in the good old days, we had things to stop the shots.
The SALT Treaty with the USSR allowed each country to put anti-ballistic systems in one place per country. The USA opted to ring the ICBM fields to have them available for retaliation against a first strike.
The USSR, who swore they would NEVER be the first to launch in a nuclear war opted to ring Moscow with ABM. Why the difference? Russia had no need to protect their missile fields as they would be emptied out in a first strike. So much for NEVER being the first to launch.
Amarillo was number ten on the list, due to the helium reserves, SAC base, and the Pantex weapons facility. Needless to say, we were well versed in Duck and Cover.