Martin Tower, the Lehigh Valley’s tallest building, isn’t a young 38.

The 21-story world headquarters of the former Bethlehem Steel was around for the company’s heyday, built in 1972 as a symbol of Steel’s might, and then became an emblem of the mismanagement that led to its demise.

That history is what developers are hoping will get Martin Tower, which is vacant and in need of many repairs, on the National Register of Historic Places a dozen years shy of its 50th birthday — the age when buildings are generally considered historic.

The designation would make the skyscraper eligible for federal tax credits and other grants to help pay for its expensive redevelopment into offices and condominiums in west Bethlehem. Public subsidies are used in redeveloping historic buildings that investors shy away from because of the cost of repairs.

The state Preservation Board agreed the tower is significant and recommended last week that it be placed on the historic register. The nomination will be forwarded to the U.S. Department of Interior for acceptance.

”Even though it’s not 50 years old, which is the typical threshold, Martin Tower tells a significant enough story about the Bethlehem Steel Corp. and its impact on the regional economy,” said Tony Hanna, city director of community and economic development.

Martin Tower, near the Eighth Avenue interchange of Route 378, has a cruciform design that created extra corner offices for the glut of Steel executives.

According to the nominating form, the tower represented corporate culture’s ”inward thinking” even as domestic competition, labor unrest and legacy costs loomed, foreshadowing the ”deindustrialization of America.”

”Martin Tower is the symbol of one of America’s mightiest industrial concerns as it plunged from the zenith of its power into a steady decline, ultimately leading to failure that resulted in the loss of over 100,000 jobs and regional economic hardship,” it says.

After Steel declared bankruptcy in 2001 and was sold to International Steel Group in 2004, there was little demand for 600,000 square feet of offices by one company. Its shape and size weren’t attractive to investors, and it needed a lot of work — possibly $16.5 million alone in asbestos removal and a sprinkler system. Martin Tower ultimately became vacant.

Developers Lewis Ronca of Wind Drift Real Estate in Bethlehem Township and media mogul Norton Herrick of Morristown, N.J., now own the building and are floating plans to turn it into a residential community. They have proposed a mix of high-end condominiums or apartments and office space for the tower, which would be surrounded by more residential and retail development.

Preserving the tower had been the key to getting Bethlehem to rezone the site to allow residential development.

Hanna said listing it on the register would help ensure it remains part of the city’s skyline.

Carol Lee of the Pennsylvania Historical and Museum Commission said the National Park Service generally accepts the state’s recommendation, but this application is ”unusual” because of the building’s age.

Buildings generally must be at least 50 so their significance can be evaluated in historical context.

While tougher, that context can be established for younger buildings, and Lee said the state board believes that Martin Tower’s petition makes a strong case.

Lee pointed to the Rohm and Haas headquarters, which opened in 1965 in Philadelphia. It is listed on the register, in part, for its innovative use of Plexiglas, a glass substitute that Rohm and Haas invented.

Other examples of historic places in the last 50 years include Dulles International Airport Terminal in Virginia and the Apollo Mission Control Center in Houston.

Carol Shull, a spokeswoman for the National Park Service, said one of the biggest benefits of the historic status are tax credits to defray expensive redevelopment costs. The status also positions the owners for state and federal grants.

Developers have already amassed at least $2 million in state and federal grants for the Martin Tower project.

”This designation makes the economics of the rehabilitation of Martin Tower more feasible,” Mayor John Callahan said. ”That, in turn, will create jobs and further investments that will ultimately grow the tax base and ensure the tallest building in the Lehigh Valley is redeveloped.”

Ronca did not return a phone call seeking a comment.

Historic credits have been used before in Bethlehem, which boasts 10 buildings listed on the register and two national landmarks, to restore old structures such as Union Station and Lehigh Riverport.