If I remember correctly, they have Caravans in Grand Frorks, Honolulu, Casper, and Salt Lake. They also fly Shorts in Honolulu. Their contracts change from time to time, so no guarantee this is still acurate. It seems like GFk is the major hiring base, but it is also their largest. The senior guys at GFK have been there 20+ years...
They also used to have EMB120's in HNL... and 3 EMB's/1 BE1900 in BQN... as well as owning Merlin Airways who operated multiple SA227's out of BQN and MIA. I think they lost the majority of that flying to AMF and MAC but I haven't worked there in a few years.