Workers broke through the wall of a forgotten vault Dec. 6 and stepped into the Allegheny County of the 1920s and '30s.

Undisturbed by light, air and touch for 70 years, the cache of trolley records discovered at Epic Metals Corp., in Rankin, offers a previously unavailable snapshot of Pittsburgh Railways Co. operations.

"This is a huge find," said Scott Becker, executive director of Pennsylvania Trolley Museum in Chartiers, of thousands of documents chronicling daily life at Pittsburgh Railways' busy Rankin Car Barn.

Epic Metals took over the car barn in the late 1960s, discovered the vault during a renovation project and gave the records to the museum. Becker said the material, still in good condition, would be cleaned, inventoried and used in the museum's mission to "preserve and interpret Pennsylvania's trolley era."

Edward K. Muller, professor of history at the University of Pittsburgh, and Joel A. Tarr, professor of history and policy at Carnegie Mellon University, called the records an exciting find.

Thanks to fare, passenger, equipment and engineering records Pittsburgh Railways filed with the state, the museum already had general information about the trolley system, at its peak nearly 600 miles of track that radiated north to Verona, Allegheny County; south to Washington County; east to Westmoreland County; and west to Sewickley, Allegheny County.

Becker said the recovered records, from 1923 to 1932, would put flesh on the skeleton, providing details he believed had been lost to history.

The cache includes employee handbooks, records of an employee relief fund, "run sheets" naming the employees assigned to each car and minutes of meetings at which company officials discussed safety and other concerns. It includes disability records detailing employees' scarlet fever, broken bones and other injuries, and reports of accidents and complaints.

Becker said the records showed the challenges of moving millions of passengers each year. In a report dated Sept. 20, 1932, the company documents a woman's complaint of rude treatment on an inbound trolley at Aylesboro and Shady avenues in Pittsburgh's Squirrel Hill neighborhood.

The woman said she arose in the middle of the block and walked forward saying "Aylesboro" but didn't know whether the driver heard her. As her stop approached, she called out again and was humiliated when he yelled back:

"Do you think I can stop on a 10-cent piece?"

The records also show the symbiosis between the trolley company and communities it served. In various letters, Kennywood lists upcoming picnics at the amusement park, giving Pittsburgh Railways time to plan service.

By the 1920s, Pittsburgh had established itself as a major metropolitan and industrial region, and the trolley linked bustling factories with workers in ethnic neighborhoods, Muller said.

But the trolley already was on its way out. The automobile had made inroads among wealthier segments of society, and construction of roads and bridges was quickening, Muller said.

While people romanticize the trolley era, he said, it didn't seem quaint at the time. Trolleys were crowded, the service sometimes unreliable, and riders of different classes and ethnic groups didn't necessarily like rubbing elbows.

Trolley company owners often were real estate speculators, too, and development of towns along trolley lines gave rise to the term "streetcar suburbs." Tarr said trolley companies, banks and politicians formed a web of sometimes corrupt relationships.

Epic Metals, a manufacturer of steel decking, has offices in Braddock and Rankin. While renovating the Rankin building Dec. 3, workers demolished a wall on the second floor, revealing a vault 6 feet high, 6 feet deep and 8 feet high, said David F. Landis, Epic vice president, and Stephen M. Potts, the company's vice president of engineering.

Three days later, workers broke into the vault by chipping through five layers of bricks on one side. Inside, they found time at a standstill.

Dust-covered documents, some rolled up, lined shelves and covered the floor. A Westinghouse light bulb hung from a long cord.

Landis suggested notifying the trolley museum or Senator John Heinz Pittsburgh Regional History Center. Potts called the trolley museum, and Becker's team of volunteers carried away the documents in 30 large cartons.

"The important thing is, they didn't get thrown out," Becker said, noting a trash bin had been placed within 50 feet of the vault.

Museum archivist Edward H. Lybarger and his associate, Tim Jones, have been examining the records at the museum's storage center.

"What's remarkable to me, the material's been sitting there for 70 years, and it's not mildewed, it's not fragile, it's not yellowed. This was entombed," Becker said.

Over the years, the museum had obtained scraps of information about the trolley company's daily operations. But until the "virtual treasure trove" recovered from Epic Metals, Becker said, the museum had nothing comprehensive and nothing centering on one period or neighborhood.

Lybarger said the museum recovered enough material for a book. Indeed, Tarr said, there's a need for additional research on Pittsburgh Railways and other trolley companies.

"Records like this could be very helpful," Tarr said, suggesting they be mined for insights into the trolley company's corporate affairs, employees' pay and working conditions and how passenger flow changed over time.

While the records cast light on the smallest details of trolley company business, there's no hint as to why Pittsburgh Railways employees closed the vault's double doors in the 1930s and walked away for good. But Lybarger believes he has the answer.

Lybarger said a work trolley, used to carry equipment and materials, damaged the old Rankin Bridge during summer 1937. With the company no longer able to run trolleys from the Rankin Car Barn, he said, the building went from an operations nerve center to a storage center.

The records are among a handful of important donations to the museum this year. Merritt H. Taylor Jr., former president of Red Arrow Lines, donated photos and documents from that Philadelphia-area trolley company, and a retired transit worker from Bethel Park gave the museum a Pittsburgh Railways streetcar maintenance manual.

"What we've seen is incredible," Becker said.