The Simple Calling sim roams all down US 95 in western Nevada (Reno to LV) on a network just identified as "roaming".

In some of the "urban" areas like Tonopah and Beatty it also roams on Commnet - which is suprising as the commnet website Commnet Wireless doesn't currently show any coverage in NV.

Interesting. I wonder if anyone has made a map showing all GSM coverage in the US (not just AT&T or just T-Mobile but a vcombined map showing those & the other operators' coverage on one map). I hear from too many CDMA buffs that CDMA 'has more coverage' than GSM and it would be nice to actually see some maps & maybe stats to do a comparison. I'm guessing that even though GSM was late to the US compared to elsewhere in the world and compared to CDMA, by now the level of coverage GSM has has to be about on par with CDMA. Sure there are likely to be some spots one has coverage and the other doesn't, but that's expected.

I can assure you that GSM isn't yet on par with CDMA in the US. It's improving rapidly but it has a ways to go.

If you'd like evidence, check out the Verizon CDMA coverage of North Dakota versus the GSM coverage provided by AT&T (almost none) and T-Mobile (none, but there is some GSM roaming coverage that CDMA provider Alltel has installed).

I'm finding that GSM is more and more usable there, but there are parts of the US where you would not want to use GSM as your primary coverage.

I wish there was a map...............
 

How many GSM networks in the USA?
 

Well I guess I will try to answer my own question. Using info from GSM World USA network page I counted 75 networks. Five are not on the 850/1900mHz frequencies, 7 are 'planned' and 3 have multiple listings for the same network. So 50 would seem to be the number of GSM networks from a easily accessed resource.

Having done some more research at GSM World one finds that some of the information is dated and some of the companies no longer exist or were bought out and then bought out again. So grain of salt is always wise.

Colorado, Nebraska, and kinda South Dakota
 

I like the direction this thread has gone. If it becomes: "Who are the obscure GSM phone companies of the USA?" that would be neat.

North East Colorado Cellular does a suprisingly good job of Colorado and Nebraska if we can believe the maps:

North East Colorado Cellular, Inc (NECCI) (Viaero Wireless) - Coverage Map

Viaero local coverage

Now, coverage in South Dakota seems a lot more iffy.
A code USA-590 gave me Western Wireless Properties which had been bought by Alltel which is being consumed by Verizon. The last two are not GSM providers but GSM World has an Alltel map:

Alltel Communications Inc - Coverage Map

Maybe there is some FCC licencing database that would show which markets are served by which companies, although it probably doesn't show the technology they use.

Like that mention of Alltel providing GSM roaming in ND, I had coverage from Unicel in Jackpot, NV (just south of Twin Falls, Idaho) about a month ago. They are now part of Verizon, so are presumably not a GSM company, but just make some roaming income by putting GSM on their towers.

BTW, apart from Reno, I haven't found anywhere else that the Simple Calling will roam on 3G. I wonder what is different about 3G in Reno?

Alltel used to be GSM and switched to CDMA, which Verizon later bought out. Alltel never converted all of their GSM towers over (likely because they could make money off roamers in areas that have no other GSM coverage).