Because of the way cellular licensing was done (two licenses in each market and 700ish markets in the country), it meant that many carriers were left with large holes in their networks over the years. Sure, later on a bunch of other license were made available, but something like a 1900MHz license isn't useful for rural coverage because the signals don't travel as far as lower frequency signals. So, in most rural communities you got the choice between two carriers. Now, some rural communities only have one real option due to mergers and the relaxation of the rule that no company can control both cellular licenses in a market.
Suffice it to say, Alltel's network in your area will soon be running UMTS/HSPA under AT&T's ownership. AT&T really couldn't enter the market without buying their way into the 850MHz licenses in the area. Alltel and Verizon owned them. Now Verizon and AT&T own them.
If you really want to see the state of rural wireless improve, write to the FCC or your state utilities commission and tell them that you want to make sure that one or two companies can't control all of the low-frequency spectrum required for rural coverage. Right now, AT&T and Verizon have merged their way into becoming the only two companies with the licences needed to provide rural coverage. Even looking at the 700MHz auction, it's clear that the situation won't change much. AT&T and Verizon took the majority of the licenses with smaller bidders getting some scraps. So, the far-penetrating spectrum is being concentrated in the hands of two carriers. If you'd like that situation to change, demand that new low-frequency spectrum go to carriers other than the big two. It's one thing for Verizon and AT&T to say that they need more spectrum in major metro areas because they have more customers. It's another thing to say that they want to have an oligopoly on the spectrum that can serve rural areas.
It sounds like they are pretty serious about expanding their network there (which is good for me as an AT&T customer that regularly travels to Rapid City).