Recently, the subject of the varying quality of pizza by region has been raised, thanks in part to discussions of Washington, D.C., which has been accused, disparagingly and incorrectly, of being unable "to produce a single decent slice of pizza."
As this website, among others, has pointed out, Washington, D.C. can indeed produce decent pizza by the slice, even if it's not, on average, as good as its New York equivalent.
In fact, speaking generally, any major metropolitan area can, with sufficient strength of will and character, and a good source of filtered water, produce a "single decent slice of pizza." (Or, speaking more accurately, a single decent pizzeria.)
Similarly, pointing to single restaurants and pizzerias is not an adequate rebuttal to charges of poor overall pizza production. The ability to support a single decent pizzeria should be regarded not as a point of pride but, if anything, as the bare minimum for qualification as an American city.
The question of regional pizza quality rests therefore not on single examples, which are often exceptions to the rule, but on the chance that a randomly-chosen pizzeria will produce an adequate-to-good slice of pizza.
For this reason, we speak of The Pizza Belt, a theory I have painstakingly constructed with assistance from various pizza experts on Twitter. [Update: There is nothing new under the sun. It has come to our attention that the food writer Ed Levine laid out a very similar theory, going by the same name, back in 2006. We were unaware of Levine's prior contribution to the geo-gastronomy of pizza when we sketched out the theory below, and we belatedly acknowledge the theory's debt to him.] Briefly:
- The Pizza Belt is defined as "the area of the United States where the chance of obtaining an adequate-to-good slice of pizza from a randomly chosen pizzeria is greater than 50 percent."
- Taken at its strictest, The True Pizza Belt runs, more or less contiguously, hugging the coast, from southern New Jersey to Providence, R.I. (The map reproduced above provides a general but necessarily inexact guide.)
- Lowering the chances to one in three, or slightly expanding our definition of "adequate," gives us The Greater Pizza Belt Area, a zone spanning Washington D.C., to Boston, Mass., going no further inland than Albany, N.Y. 
- Chicago is not in the Pizza Belt. I have no desire to discuss Chicago-style pizza.
- Neither is San Francisco, for Christ's sake.
- Indeed: Beyond the Greater Pizza Belt Area is a wasteland. In most parts of California, for example, the chance that a randomly-chosen pizzeria will produce adequate-to-good slices of pizza is close to one in eight; in Los Angeles it is lower than one in ten. Here, there is bad pizza—in the vast wilderness, in الربع الخالي. We do not speak of it.
The Pizza Belt is the final word on regional variations in pizza quality in the United States. No further blog posts or discussions regarding the topic will be allowed from now on. Pizza-related opinions from people born and raised outside of the Pizza Belt are particularly unwelcome and will be dismissed with prejudice.
This weekend, in Kingston, N.Y., I had a better-than-adequate slice at the first place I saw, a pizzeria called Primo (not to be confused with the chain). Such is the magic of the Pizza Belt.
Again: A city's location in the Pizza Belt is not determined by the question "Is it possible, given a research and travel budget, to obtain a good slice of pizza in this city?" The Pizza Belt is a scientific concept based on mathematics. You cannot disprove it by sending me to specific pizza places: All that proves to me is that your city is a major metropolitan area, and that you do not understand simple rhetorical and probabilistic concepts.
Those born and raised inside the confines of the Pizza Belt, spoiled by its riches, often confuse "adequate pizza" for "bad pizza." This is from whence complaints like the above—that Washington, D.C. cannot produce "a single decent slice"—arise. There is plenty of adequate pizza in Washington D.C., and some good pizza. Only those weaned on the pizza of New Jersey or Connecticut, and who have never encountered the horror of الربع الخالي, misunderstand that pizza as "bad."
Los Angeles, it goes without saying, is in the great southwestern Taco Belt, which is of course the subject of a different discussion.