William “Wild Bill" Donovan was the wartime head of the Office of Strategic Services, the precursor to the Central Intelligence Agency. He is seen in his office during World War II. (National Archives)

For a few former spies, it was one last mission: protecting the birthplace of the country’s modern intelligence apparatus from being bulldozed in Washington’s pell-mell development. This month, they pulled it off when a small cluster of Foggy Bottom buildings, where early agents invented the pencil pistol and other tricks to bedevil Hitler, was listed on the National Register of Historic Places.

The Observatory Hill site not far from the Kennedy Center was the wartime headquarters of the Office of Strategic Services, the precursor to the Central Intelligence Agency, and had been slated for redevelopment as part of a State Department expansion.

Planners had promised a measure of protection for the place where William “Wild Bill” Donovan led a swashbuckling band of spies, but former agents were shocked to learn that it enjoyed no formal preservation status.

“I just assumed a place of that stature would automatically be protected,” said former OSS and CIA agent Hugh Montgomery, 93. Sent behind German lines by his handlers at the beginning of his 63-year intelligence career, the nonagenarian former spy came out of retirement to push for the historic listing, writing letters to lawmakers on Capitol Hill and sitting through meetings.

The former OSS headquarters on Observatory Hill in Washington. (N/A/OSS Society)

“It’s finally happening,” Montgomery said.

OSS partisans said it was a timely victory when they learned this week that the long process had landed the old HQ on the National Park Service’s latest list of historic properties. The intelligence community that traces its pedigree straight back to the little Beaux Arts campus came under fire intermittently from then-President-elect Donald Trump for its analysis that Russia had interfered in the recent U.S. presidential election process.

“At a time when the intelligence community finds itself embroiled in controversy, it’s important to remember its roots in World War II, when the world faced the greatest threat it has ever known, in the form of Nazi Germany,” said Charles Pinck, the son of a former agent and president of the OSS Society, an alumni group. “Their descendants today are carrying on the OSS legacy by fighting terrorism around the world.”

It could be that the understated compound overlooking the Potomac, the one-time site of the Heurich Brewery, was too clandestine for its own good. It is clearly visible to drivers and concertgoers, but even many neighborhood residents and local preservationists were unaware of its history as the place where modern American spycraft was first honed.

Donovan, whose office in room No. 109 is preserved as a memorial, built a team of cryptographers, analysts and spy handlers. Montgomery said the secret orders he received were often simply signed “109.” German-born actress Marlene Dietrich received briefings at the site before her morale-building tours of U.S. combat units. Julia Child was a file clerk at the office before she became an overseas operative.

After the war, the agency pivoted to fighting the Cold War and then morphing into the first headquarters of the CIA. Later spy chiefs Allen Dulles and Richard Helms both worked at the Observatory Hill compound.

When the federal government announced plans to remake the whole area for use as State Department offices, intelligence alumni and preservationists went into action. Nothing short of formal listing on the register would offer enough protection, even though officials said they were committed to keeping the appearance of the main spy buildings intact.

“This is a very important place,” Mina Wright, the General Services Administration’s director of planning and design, said in 2014. “We are totally dedicated to protecting the sense of history here, which will depend on the successful integration of the old and the new.”

The GSA did not immediately provide a response to the site’s listing on the National Register. Pinck said the GSA and State Department were supportive of the preservation efforts. He and his band of aging spooks said they feel the HQ is now safe. Mostly.

“I guess now it’s protected from anything except an earthquake,” Montgomery said.