Much has been written about 1969 as a year of upheaval and social change. But in 2009, when home mortgage foreclosures and global warming pose major threats to our society, looking back another 20 years may prove more valuable.

In 1949, President Harry Truman convinced Congress to break with the past and inject the federal government into process of developing cities and financing housing. The 1949 Housing Act expanded the availability of federal insurance for home mortgages, igniting the growth of new suburbs farther and farther from the centers of our cities.

Together with federal highway funds that came a few years later, the 1949 law started what we now describe as “suburban sprawl.” The two initiatives put Americans on the path of long commutes, heavy traffic, air pollution, water shortages, and a long-term increase in carbon dioxide emissions, which fuel global warming.

Policymakers and the general public are starting to recognize how that pattern of development hurts the environment and puts our climate at risk. With the home mortgage foreclosure crisis, the impact of sprawl on household finances has become crystal clear. Traditional mortgage underwriting considers only costs for shelter. But as the cost of housing rose, more and more families had to live farther and farther from their jobs to afford homes. The cost of transportation combined with mortgage debt forced many of these families into foreclosure.

The time has come to declare that the “General Motors model” of urban planning is officially bankrupt.  We must reinvest in existing urban centers, because reusing the infrastructure and restoring underutilized real estate is far more environmentally efficient than new construction, no matter how green that construction is. It’s also time to change local land use laws to promote more compact development around transit and the availability of affordable housing close to jobs and services.

The Obama Administration is moving in this direction by beginning to coordinate federal housing and transportation policies that encourage more compact, transit-oriented development. It has created a White House Office of Urban Affairs and laid out six livability principles to guide housing, transportation, and environmental policy. It is working on ways to measure housing and transportation costs that would allow mortgage bankers to offer a “location-efficient” mortgage.

Senate Banking Committee Chairman Chris Dodd has proposed a major new federal program of grants to help local governments formulate regional plans for growth around transit corridors.

Federal money and policy leadership help a lot.  But the federal government has limited power to change local decisions governing land use and real estate development.

A reversal of the ill effects of sprawl will take committed local officials who are willing to change land use policy and zoning even in the face of resistance. Architects, real estate developers, bankers, and city planners must collaborate to create vibrant urban spaces that meet consumers’ needs.

In California, that’s exactly where we are headed. The state legislature has unleashed the biggest change in how communities are shaped and land use is planned since highway construction took off in the 1950s.  A recent state law relies on the transportation planning process to focus the attention of local leaders on climate change, land use, zoning, and the need for affordable housing. State legislators hope that transportation spending will spur community cohesion and efficiency instead of encouraging more sprawl.

It will be years before there is a measurable reduction in the environmental damage of sprawl, and it’s unclear how quickly other states will follow California’s lead. But there’s no turning back: Americans have begun the long process of changing land use patterns and rethinking how and where we live.

Change won’t come easy. Americans still value big houses with big yards. They don’t want to conserve water or cut back on how much they drive. But many understand that the issue is not just about the environment but about how we live and how we connect with each other.

Many residents of today’s faceless “sprawlburbs” realize that they are missing out on the connections and richness of real communities like the ones our parents and grandparents inhabited. More Americans are starting to seek out places in which to gather and attractive streets and parks in which to stroll to the store and mingle with their neighbors.

If the outer limits of sprawl have indeed been reached, and if we begin to look back toward the urban cores, there is hope for even the most distressed cities to make a comeback.

The harder question is whether Americans can deal with environmental challenges and at the same time honor the most fundamental promise of the 1949 act: that every American family have “a decent home and suitable living environment.” This poses a huge challenge, but more compact development that reduces energy costs and commuting costs moves us a step closer toward finally fulfilling that promise.

Andre Shashaty is president of the Partnership for Sustainable Communities (www.p4sc.org), a national nonprofit organization based in San Rafael, California.