Fannie Mae has discovered 53 stealth cities rapidly growing under the radar.

By Christina B. Farnsworth

Everybody's heard of Phoenix, but how about Chandler, Gilbert, Glendale, Mesa, Peoria, Scottsdale, or Tempe? A report released in June by the Fannie Mae Foundation claims these "boomburbs" are bursting onto the sprawl scene.

Each of these cities surrounds Phoenix, and as a group comprise more than 42.2 percent of the Phoenix area's inhabitants, making the city the No. 1 U.S. boomburb.

Fannie Mae's report, "Boomburbs: The Emergence of Large, Fast-Growing Suburban Cities in the United States," defines a boomburb "as an area that has more than 100,000 residents and has maintained double-digit rates of population growth in recent decades but is not the largest city in its metropolitan area. Boomburbs differ from traditional central cities and older satellite cities in that they almost always lack a dense business core. Their housing, retail, entertainment, and offices are spread out and loosely configured."

This definition notwithstanding, the concept of a new type of suburb isn't completely understood. "The boomburbs are elusive and not yet fully part of the public policy debate," says Stacey Davis, president and CEO of the Fannie Mae Foundation. "They are complicated places with potentially big problems, such as lack of affordable housing, traffic jams, spread-out development, and strained public services. But they also present opportunities for cities and suburbs to find regional solutions to their common challenges."

Incredibly, some of the boomburbs described by Fannie Mae are so large they exceed the population of actual cities. Mesa, Ariz., for instance, with its nearly 400,000 residents is the largest boomburb, boasts a larger population than Minneapolis, Miami, St. Louis, Pittsburgh, or Cincinnati.

Fannie Mae's view is not the only take on sprawl. A Brookings Institute study released in July measures sprawl by comparing population growth to developed area growth. And by that measure, the Phoenix metro area is managing sprawl well: Population increased 72.9 percent, but the developed growth area increased by only 41.8 percent.

Chicago, on the other hand, had a population growth of 9.6 percent but had an increase in developed growth area of 29 percent. Dallas had a pretty well balanced population growth of 49.1 percent with a developed area growth of 54.4 percent. The Brookings report suggests that sprawl at the fringes of metropolitan areas is leaving hollowed-out urban cores, or "donut growth."

An interesting trend that has emerged along with boomburbs is the rise of homeowners associations as governing arms. Often what makes suburbs grow exponentially is the addition of master planned communities to the housing mix. These large-scale projects often dominate boomburbs and are frequently led by homeowners associations that act as small private governments and take the place of municipal government. Thus, the boomburb political dynamic is often between city hall and the homeowners association rather than city council members and voters.

The real question now is whether the boomburb phenom will continue, especially when you consider how they grow (generally out rather than up). While it's true some boomburbs have annexed land to expand their populations, others are land-locked just like the cities they surround and are near the point of being full (based on their current land use plans). To grow more, these areas will have to change their land use patterns to accommodate higher density.

Fast Facts

Of the 53 boomburbs, four top 300,000 in population, eight surpass 200,000 and 41 exceed 100,000.

Boomburbs accounted for 51 percent of the past decade's growth in municipalities between 100,000 and 400,000 people. Municipalities in this class size gained 4.1 million new residents during the 1990s, 2.1 million of whom live in the boomburbs rather than in central cities.

Boomburbs often have more diverse populations than smaller suburbs.

Bloomin' Burbs
Boomburb Metro Summary
Rank Metro area Number
of boomburbs
Metro boomburbs
Percent of metro
population in boomburbs
1 Phoenix 7 1,371,159 3,251,876 42.2%
2 Los Angeles 18 2,963,724 16,373,645 18.1%
3 San Diego 3 468,144 2,813,833 16.6%
4 San Francisco 4 586,389 7,039,362 8.3%
5 Denver 3 521,459 2,582,506 20.2%
6 Miami 3 481,395 3,876,380 12.4%
7 Tampa, Fla. 1 108,787 2,395,977 4.5%
8 Chicago 1 128,358 9,157,540 1.4%
9 Las Vegas 2 290,869 1,563,282 18.6%
10 Portland, Ore. 1 136,924 2,265,223 6.0%
11 Dallas 7 1,323,908 5,221,801 25.4%
12 Salt Lake City 1 108,896 1,333,914 8.2%
13 Norfolk, Va. 1 199,184 1,569,541 12.7%
14 Seattle 1 109,569 3,554,760 3.1%
Total   53 8,798,765 62,999,640 14.0%
Source: Fannie Mae Foundation