With more than half of all U.S. mobile phone buyers picking smartphones, we're all relying heavily on wireless Internet. Seven major U.S. wireless carriers are all promising some form of "4G" now or in the near future, but all 4G isn't the same. So for the third year in a row, we sent drivers out to see the state of the 4G nation and bring home 240,000 lines of data to figure out which network is the fastest near you.

This year we dramatically expanded our testing project, taking three 2013 Ford Taurus cars out to survey 30 U.S. cities. We tested the five largest U.S. carriers: AT&T, MetroPCS, Sprint, T-Mobile, and Verizon Wireless. (For more about the wireless providers, see Different Carriers, Different Strengths.)

We found the situation is even muddier than it was last year, as all the carriers seems to be calling nearly everything 4G. We'd love to say that LTE is the gold standard, but that isn't always the case, as the slower results from MetroPCS's LTE network and the speedy downloads on T-Mobile's HSPA+ 42 network show. (For more about 4G classification and speeds, see How Fast Is 4G?)

Rather, you need to have a solid LTE network with lots of spectrum to win, and it helps if not a lot of people are using it yet. Across our 30 cities, Verizon's 4G LTE network dueled with AT&T's new 4G LTE network for supremacy; Verizon won 19 cities while AT&T won 10, and the two carriers tied in one. T-Mobile came surprisingly close for a non-LTE carrier. And the slower results in cities where AT&T and T-Mobile have less spectrum show that the spectrum crunch is real. (For more, see Why Spectrum Matters.)

Not all phones, including Apple's popular iPhone, support 4G, and the fastest technologies aren't available in rural areas, either. So we made sure to measure the carriers' 3G networks as well. (For more, see Which Carrier Has the Fastest iPhone?)

Finally, this is a snapshot of networks in May 2012. Our results are sure to change in 2013 as new LTE networks come on line from Cricket, Sprint and T-Mobile. We got a brief glimpse of what Sprint will have to offer in Atlanta; for more on that, see Testing Sprint's New 4G LTE Network.

Our Methodology
We chose our 30 test cities so they were evenly spread across our six regions, and so we could drive to all of them in three weeks. We also chose so as many of them as possible had the maximum number of 4G networks. We tested 12 of MetroPCS's 14 LTE cities, 20 of AT&T's 39 LTE markets, 23 of Sprint's 70 WiMAX markets, and 30 of Verizon's 258 4G LTE markets.

Two of the carriers we regularly review declined to participate this year. Cricket currently runs a slow-but-steady 3G network and is installing 4G LTE soon; it'll return in our 2013 feature. U.S. Cellular has LTE, but its coverage map didn't mesh well with our travel plans.

The competition is much closer than it looks. Calculating our speed score, we applied a major penalty if a network wasn't available in one of our test cities. If we only counted the cities where AT&T LTE had coverage, it would have tied Verizon nationally and won the northeast, southeast, and south central regions. But you can't win if you don't play, and AT&T's 39 markets pale when compared with Verizon's 258-market rollout. (After our testing was complete, AT&T disputed the upload speed results we found on its network.)

Note that we didn't test call quality, dropped calls, or coverage. These tests are all about data speed. For the best assessment of voice call quality according to our readers, check out our annual Reader's Choice awards results. To get a picture of wireless coverage near you, download the Sensorly app from the Android Market and you'll see crowd-sourced coverage maps for all the major U.S. mobile carriers, enhanced with the data from our test drives. (For more, see How We Tested.)

Again, mobile networks are constantly changing, and almost always for the better. And because speeds vary based on tower location, network load, device used, and even the weather, we can't predict performance in a specific location; rather, we're giving a snapshot of a few days' worth of usage in several locations across a metro area. Hit the next page for the regional and national winners: