People love to beat up on the Postal Service these days. But for community developers like LISC, working to help local citizens improve their neighborhoods, the beleaguered mail carrier has turned out to be a surprising boots-on-the-ground ally. Take a look at Buffalo. This once-booming city on the Great Lakes has become a symbol of Rust Belt decay, with its vanished industrial base and dramatically declining population. It's been on the ropes pretty much since Ike was president but it is just the kind of place community developers are itching to help. And their first order of business is to figure out which neighborhoods have a modicum of hope. How do we do that? The citizens tell us, by the streets they choose to live on and the streets they choose to leave. Yet when you walk cold into a neighborhood with one neglected house after another, it isn't easy to tell if a home is occupied or empty. You can't go up and knock -- it isn't practical or safe. Some are drug dens. Gangs make the rules and bodies occasionally turn up behind closed doors. But these are the same streets that mail carriers walk six days a week. When you think about it, they are nothing short of local heroes. One day several of us from LISC's Buffalo office were standing on a long, dead-end, weed-strewn block. Not a soul was in sight. One house had a hole in the roof and a six-foot tree growing up out of it. We had no idea who, if anyone, was living there. Just then a mailman came along and parked his little jeep at the end of the block. We had our guide -- this was one federal employee who would know. It turns out that over the years the U.S. Postal Service has had an agreement to give the Department of Housing and Urban Development lists of houses where no mail has been collected for at least 90 days -- "undeliverable" addresses -- four times a year. This was an information gold mine for us -- much more current and accurate than the once-a-decade census data we were sifting through. We started studying the postal service numbers and with the mail carriers' help, we began to see trends. Nearly every census tract in Buffalo was losing people. On the dead-end block where we stood that day, there had once had been 60 homes; now there were 27. Nine were occupied, all by renters. We wondered how we could help those nine families. Then we started asking the people there. One guy said flat out that the place was unsalvageable. He told us his little girl was playing at a house across the street with a dead cat in the yard. "This one's gone. Get me out of here," is how he put it. The only help he and his neighbors wanted was an escape route. Using information from mail carriers, we began to identify Buffalo neighborhoods where we could do some good. It would be nice to rescue every street, but resources are scarce in this line of work. In Buffalo, and in 30 cities and dozens of rural communities, LISC aims to put what public and private money we have into places that will yield the best return-places where the residents themselves see a future, where small businesses will be willing to locate, places near hospitals and transportation routes. With our help, 500 residents and businesses in one Buffalo neighborhood joined to form the Westside Community Collaborative. Churches teamed up. Realtors came back. We got hold of some federal stimulus money and turned vacant lots into community gardens, one of which is raising fish. On two short blocks ten vacant houses were targeted for renovation. Already six of them are finished and sold. Eleven more rental units will be ready this summer. There's a waiting list. All across America, community developers are looking for ways to make sure low-income people -- the working poor and the unemployed -- don't drift off the social monitor while the focus turns to the strapped middle-class. Progress is possible in even the most destitute places. The agreement between HUD and the postal service expired at the end of 2010, but was recently revived. We're glad they brought it back. For the people of Buffalo, it's often been two steps forward and one step back, but we're moving in the right direction. Those "undeliverable" numbers aren't always perfect, but they lead us to the people who haven't given up, and that's a good start.