Philadelphia rode the Reading Railroad into the forefront of the Industrial Revolution in the 1800s. The tracks carried coal to heat the city's homes and to power the factories that produced everything from machine parts to Stetson hats. But that prosperous era ended even before 1984, when the last train rode on the tracks. In ensuing years, the abandoned rail bed became covered with weeds and garbage. Warehouses, factories, and housing stock slipped further into disrepair.

The neighborhood started turning again when developers carved up industrial buildings into loft apartments in the 1990s. And now, the elevated rail bed's remains are being turned into a Rail Park, which just might help forge a new identity in a string of unconnected neighborhoods.

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The first phase of the Rail Park, starting at Broad and Noble Streets and running east to 10th and Callowhill Streets, opened to the public this month. The quarter-mile stretch took eight years to raise the money, acquire the land, and build. It cost $10.3 million, with almost $7 million coming from the state and city, and the rest donated by foundations and almost 300 individuals, a sign that there's a high level of enthusiasm for the park.

Plans for a second phase are still being worked out, but it's likely to continue east, dip south to 11th and Vine Streets and north to Ninth Street and Fairmount Avenue. Planners don't yet know how long it will take to complete and the best guess on cost is about $12 million. Subsequent phases would run west along the old track bed just north of Callowhill Street from Broad to 21st Streets and then up to 31st Street and Girard Avenue.

Yet, with all the city's needs, like a stubborn 26 percent poverty rate and epidemics of gun violence and opioid abuse, it's worth asking whether this is the best use of  the city's public and private resources. One part of the answer may lie in how the park and neighborhoods evolve.

The hope of Rail Park proponents is to use the park to help link the neighborhoods together, which are growing in an area with little green space and more suited for industrial than residential uses.

Adding an attractive amenity like a park or trail to a neighborhood typically spurs development, and increases in housing values as demand pushes up prices.  That can squeeze out all but a few who can afford it.. The rail park gives the city has an opportunity to demonstrate what it's learned from gentrification to get it right.

Paul Levy, head of the Center City District, which raised money and developed the park, estimates that about one-third of the land near the park is vacant.  That should be enough to accommodate market rate and affordable housing. The city can create special zoning that allows developers to build more dense projects if they provide affordable housing. It can target funds from construction in the zone to the Housing Trust Fund to ensure that affordable housing stands alongside luxury townhouses and lofts. That can help the area become Philadelphia's next great — and equitable — community.