The U.S. military has 425 bases around the country, and by mid-May, will have to come up with a list of which ones to shut down. It's part of the Pentagon's plan to save perhaps tens of billions of dollars by eliminating and consolidating underutilized bases. But, states and cities are lobbying furiously to keep their facilities off that list. Previous rounds of base closures have been devastating to some small communities, like Vallejo, California, which was once home to Mare Island, the oldest Naval shipyard on the west coast.

After it opened in 1854, the Navy built everything from wooden ships to nuclear-powered submarines here. At its height during World War II, it employed some 40,000 people. But by the time the base closed in 1996, only about 20% of those jobs were left. And today, nearly a decade later, only about 1,800 people work on the island, and Vallejo is still struggling to recover.

The community's downtown is a very different place now than it was when the base was still operating. It actually began losing businesses to suburban malls in the 1970s, but Mare Island's closure was the final blow. Today, there are boarded up stores on every block, and not much street traffic and vitality during what should be the busy noontime lunch hour.

Rick Wells, president of the local Chamber of Commerce, compares the economy to a professional sports team. "Our economy lost its star player," he says. "The Navy provided thousands of jobs in this community and when those jobs left, our star performer in the local economy left as well."

Without sailors and their families in the community, businesses that served them, from dry cleaners to restaurants, went under. Real estate prices plummeted as well. James Spagnole, who directs California's Office of Military and Aerospace Support, says Vallejo's story is typical of many small military towns. "In a small community, the movement of a large base causes huge economic impact, he says. "In a large, diverse community, the economic impact, even if the base is large, might no be so keenly felt."

In other words, when a base in Philadelphia or San Francisco closes, it's only a sliver of the overall, local economy, and the city marches on. But in Vallejo, city leaders say the recovery process could take up to 3 decades.

Part of the problem, according to Mr. Spagnole, is that military bases often require extensive clean-up before they can be used for other purposes. "In the war years, in World War II and Korea," he explains, "the naval shipyards and some of the airplane factories were committed to producing ships in huge quantities. And the result was that while they were well-meaning and did not even realize it, they were impacting the ground, the water and the surrounding areas."

Fuel oil, battery acid, and even old artillery shells have been found in the ground of Mare Island. Old cranes stand rusting along the dockside, relics of a bygone era. There are dozens and dozens of dilapidated and abandoned warehouses on the island, contaminated with asbestos and lead-based paint. More than 500 buildings and structures are historic landmarks, so they can't simply be torn down, and no one knows how long cleanup of the whole island will take. In the meantime, there are signs posted around the island, warning people to stay off certain roads, avoid walking through some fields, and keep away from old buildings.

Myrna Hayes, the community representative for the Mare Island restoration advisory board, points to one site. "Here we have a pocket of contamination behind chain link fences that's right smack in the middle of the developers planned housing developments," she says, shaking her head. "It isn't very attractive and it isn't very comforting to those people purchasing homes nearby to see a sign on a fence that says this building site contains PCB's."

But Vallejo does have one thing going for it. It's just across the bay from San Francisco, where housing is scarce. So, when 2,000 hectares of land suddenly becomes available, even on a dirty military base, developers see dollar signs.

Construction on new homes began last year. Fifty-five residences - going up in an area that's been cleaned - have already been sold. And 3,000 people are waiting in line for the next set of homes. About 75 businesses have recently moved back onto the island. And Vallejo City leaders and the Chamber of Commerce say the economic recovery is well underway. They're hoping when Mare Island comes back, downtown will rebound as well.

They're trying to do their part in the revitalization by planning more downtown housing and open spaces, and waiving permit fees for new business tenants. They're also trying to advertise Vallejo as an affordable commuter town for people who work in San Francisco, which is just a 50-minute ferry ride away.

But Mayor Tony Intintoli admits, the city has a long way to go. "For many years we were a Navy city. That's no longer the case," he says. "So, one of the challenges is to redefine the city, give it a new identity and answer the question, who are you? And what are you? And what do you want to be?" Those are easy questions to ask, the mayor says, but difficult to answer.