Evanston Air National Guard Base has not been mentioned so far in the Gone series. It will probably have relevance in the books to come.
In Plague, while Sam, Dekka and Jack go on a mission to find Lake Tramonto they discover the National guard base. They go in and find a boy Toto who has apparently been alone for a very long time feeding himself on nutella. They ask him from where does he get it and he shows them a train full of Nutella, Pepsi, Cup-a-noodles, mac laptops and the most devastating discovery was a cartload full of shoulder-fire missiles. While exploring the office of the national guard base, Jack discovers a leaflet which contained several names of people who had or were developing powers. They are Toto the truth-teller, Darla (who can go through walls, and who was taken away before the FAYZ), Sam, Caine and Taylor. Sam is angry that the government knew about the events of Pardido Beach back before the FAYZ and kept it a secret to everyone.
In Fear the guard base is only mentioned when Bonnie and Blake have used old reference books and out-of-date documents as toilet paper for the kids at the Lake.