If you're curious about the best and worst cities for cellular connectivity in the U.S., then you've come to the right place.

The lowdown
Seattle-based RootMetrics has provided us with data covering 3G and 4G networks from the top five carriers in the U.S. The data comes from the top 75 urbanized areas in the country, based on results from a downloadable speed test app.

For a quick taste of what's to come, here are the fastest cities in the U.S., according to RootMetrics, which averaged the download speeds in a given place for each of the top nationwide carriers and determined an overall ranking for each city:

Table 1: Five Fastest Cities (All Carriers)

Table 2: Five Fastest Cities (Top 4 Carriers)

Not all 4G is created equal
It should be noted that AT&T Inc., Leap Wireless International Inc., MetroPCS Inc., Sprint Nextel Corp. and Verizon Wireless all run some form of 4G Long Term Evolution (LTE) network in the U.S.

T-Mobile USA, meanwhile, uses a fast form of 3G technology called High-Speed Packet Access-Plus (HSPA+), which it markets as 4G. AT&T also sells HSPA+ as 4G alongside its younger -- but growing -- LTE network.

T-Mobile is expecting to introduce LTE in key metropolitan areas in 2013.

Not all 4G is created equal. AT&T and Verizon have wider radio channels to deploy LTE technology than the smaller operators do, so those networks tend to be the fastest.

As you'll see, AT&T or T-Mobile's HSPA+ networks can give the 4G networks a run for their money, particularly in the cases of Leap and MetroPCS, because those carriers have much less spectrum -- meaning smaller channels overall -- to deploy 4G LTE in.

Verizon also has a significantly larger 4G LTE footprint than any of its rivals. As of late October 2012, Verizon has 419 LTE markets live, AT&T has 77, Sprint has 32 and MetroPCS has 13 cities and parts of Florida, while Leap just has two cities up.

The methodology
RootMetrics went about the tests like this:

• RootMetrics visited a number of markets twice in 2012. For the five fastest and five slowest markets for each carrier, they did not average both visits, but rather considered each distinctly. Dates are provided to indicate when in the year a fast or slow test speed was recorded.

• To determine the overall fastest and slowest cities, the company took each carrier's average speed in a given market and averaged all of them. This measurement does not necessarily say anything about an individual carrier. Carrier A could still be very fast in a "slow" market because all other carriers are slow.

• The testers have provided two types of maps: One that includes all six carriers tested, and one that includes only results for AT&T, Sprint, T-Mobile, and Verizon. The latter is offered to screen out exceptionally slow speeds from Leap or MetroPCS.

• Remember that this data incorporates both 3G and 4G carrier networks that offer a wide variety of speeds.

Ready? Here are the results (free registration required):

• The Fastest Wireless Cities Across the U.S.
  
• The Slowest Wireless Cities Across the U.S.
  
• The Best & Worst Cities Overall

Dig in to the data and let us know what you think on the boards below.

— Dan Jones, Site Editor, Light Reading Mobile