Properties so designated are in such disrepair the only way to render them safe is typically through demolition.
As of March 1, the city Department of Licenses and Inspections had labeled 585 commercial and residential buildings "imminently dangerous," including Old City's Shirt Corner, which collapsed Thursday while undergoing demolition.
And they cannot say how many of them are occupied.
The Shirt Corner was being taken down by its owners. That's unusual with dangerous buildings in Philadelphia. Only a small number of owners go through the expense of taking down a building that has been long ignored. The city typically bears the cost of neglect.
But officials say with only $6 million budgeted, they can't raze all that should be taken down.
"It's a matter of resources," L&I spokeswoman Rebecca Swanson said.
The typical demolition costs $15,000, and the city has a long list of properties at risk of collapse.
The department expects to receive an additional $3 million this fiscal year to make up for some larger unexpected demolition costs, such as at St. Bonaventure Church in North Philadelphia, where the expense is nearly $1 million. L&I officials want an additional $9 million in demolition funding for fiscal year 2015.
The number of buildings listed as dangerous is similar to the number demolished last year - 536 by L&I and 53 by private owners.
Once a building makes the list, code enforcement officials can order the owner to fix it or take it down.
If the owner ignores the notice, the city can pursue the matter in court or take down the structure on an emergency bases and place a lien against the property.
But the city often finds there is no viable owner to hold responsible, Swanson said.
"Most don't have owners," she said. Homeowners listed on two of the Euclid Avenue properties have died.
The city is in litigation with 47 property owners to fix or demolish buildings deemed imminently dangerous or unsafe, a less severe designation, said Scott Mulderig, director of L&I's emergency services and abatement division.
Some of those properties are inhabited, but Mulderig could not say which ones.
That information is not searchable in the L&I database, Swanson said. "There would be notes" in each property's file that would describe an occupancy.
When occupants refuse to leave, police can remove them and charge them with violating an order to vacate. A court order is required to evict a homeowner.
Though many of the properties on the city's "imminently dangerous" list are sealed to prevent entry, others appear to be home to someone.
On Friday, a few chairs sat on the porch of a house listed as imminently dangerous in the 2600 block of North 29th Street.
Three newspapers lay scattered by the entrance. Curtains in the second- and third-floor rooms were visible from the street.
The property-tax payments were up to date, and there was even an overpayment of $38 listed on the city's revenue website.
But L&I records show that on agents' last visit in May, there was no indication the house was occupied. The property, its brick facade bulging over the front porch, has been listed as imminently dangerous since July 2012.
The city prioritizes properties marked for demolition by location - especially if they are near schools, on a corner, or have occupied neighboring properties.
But residents on Euclid Avenue want the city to pay better attention to their neighborhood.
"They rush to Center City; they don't do anything in the regular neighborhoods," Andre Bradley said as he carried trash to the curb.
Block captain Theresa Nelson says she has learned to deal with the crumbling eyesores.
During the street's summer block parties, "I just tape them off so the kids won't go there."
She expects she'll have to do that again this summer.