Listserv and majordomo, phpList, GNUmailman, all these work well. Listserv is the granddaddy, but the others have significant followings. Any hosting provider should have one or more of these in their list of "standard supported" apps that you can run on their servers.

The counties with the sudden increase in income match up with the Bakken oil patch. This is a decent article with a map to illustrate

Sadly, the oil will be extracted, the land will be poisoned, and the workers will leave for another boom and/or gold rush elsewhere, so the counties will be no better off unless they tax the oil extraction effort now.

Except for Joseph Nacchio of Qwest, who openly defied the NSA in 2002, and demanded a court order. He was then prosecuted for "insider trading" for selling some stock just before the US government pulled all Qwest's contracts as revenge for helping to expose the program of illegal surveillance. Nacchio was a hero, and no one even noticed. http://www.usatoday.com/news/washington/2006-05-10-nsa_x.htm