What separates a trend from a fad? We pondered this question as we dug through 25 years of anecdotes and experience, looking for the building industry's most momentous changes.

Many of those changes tie directly to new technology. Air conditioning has drastically increased population in southern states. Homes everywhere have become tighter and more energy efficient— less forgiving.

America's changing social fabric has wrought other changes. Many more women entered the workplace. Baby boomers grew older and wealthier, moving into ever larger homes. Interest in traditional neighborhoods re-emerged.

Through all of these changes, builders had enormous influence. If "the past is necessarily inferior to the future," as one Italian futurist suggested back in 1911, imagine the surprises likely in the next 25 years.

Here to Stay

Decades ago no one had yet heard the words traditional neighborhood development (TND) strung together like a developer's rosary.

The scene: 1981. As the prime rate approached credit card levels, buzz started to spread within the development community over a picturesque new town in the Florida panhandle. Seaside— its traditional home designs, porches, and easy walks to neighborhood stores— an icon for a new way of life in new-home communities.

The Walton County, Fla., resort, planned and designed by Andres Duany and Elizabeth Plater-Zybeck, became a poster child for the neo-traditional design movement and served as the inspiration for hundreds of similar neighborhoods during the next 20 years.

TNDs spurred formation of the Congress for New Urbanism (CNU), the San Francisco-based nonprofit founded in 1993. CNU works with architects, developers, and planning professionals. It teaches them how to implement the principles of new urbanism, which include coherent regional planning, walkable neighborhoods, and attractive, accommodating civic spaces.

New communities large and small hoisted the TND banner— mind if they actually exercised principles of pedestrian scale. Alleyways, narrow streets, sidewalks, and accessory apartments became prized community features. Planning officials jumped on the bandwagon, sometimes writing new rules to allow TNDs, sometimes just making exceptions.

Harbortown, a traditional neighborhood developed by Henry Turley in Memphis, Tenn., in the early '90s, proved the power of the concept. When architects Looney Ricks Kiss had previously sought approvals for similar projects, officials wouldn't budge. But they allowed them in Harbortown, which became one of the most widely celebrated projects of the last decade.

Seaside prospered in the face of parody as the set for the movie "The Truman Show." By the mid-'90s, Cooper Robertson & Partners and Robert A. M. Stern led a team of architects, including Cesar Pelli, who planned and designed the Disneyland of TNDs, Celebration (one of America's few TNDs with enough tourists to float retail).

TNDs answered the boomers' desire for variety in housing design and smaller neighborhoods. Yet, the broad consumer response critical to successful TND commercial centers has proved elusive.