Most get there by private vehicle. One absolutly stuffed with humanity. In our neck of the desert, far away from your nirvana, it is not uncommon to hear of 14 or 17 illegals spewing all over the road in a roll-over accident.
People on this thread seem to be having difficulty with language or logic or both. You asked, "How do you think the illegals in Massachusetts, Minnesota and Wyoming get there?" You didn't ask how they get to, or across, the border. Few are being driven from near the border to Massachusetts &c., in private vehicles. (Such rollovers as you describe just do not happen on the long drive north, do they?)
ML/NJ