Mark Johnston, center, is co-nominated for a Service to America Medal for his work with the Homeless Veterans Initiative. He is pictured with Laure Rawson, right, Director, Housing Voucher Management and Operations Division, and Ann Marie Oliva, Director, Office of Special Needs Assistance Programs. They are pictured in Washington, D.C. under a bridge that Johnston walks under daily. He has helped three homeless men who lived under the bridge. (Sarah L. Voisin/WASHINGTON POST)

Mark Johnston, fresh out of graduate school, took a job with the Department of Agriculture in 1983 on a hunger commission working out of the White House. On his way to work one morning, he saw a man sleeping on a grate just outside the White House compound, apparently homeless.

“I went up to him and asked, ‘What are you doing here?’ ” Johnston recalls. “There was a shelter that had just opened up, so he didn’t need to be on the street.”

The sight of the man in such obvious poverty just yards from the seat of American power made a strong impression on Johnston. He paid him regular visits over the next two years, bearing food and clothing, until one day the man disappeared.

Across the country in California, Susan Angell was getting to know a different kind of homelessness: that among military veterans.

Angell had just secured her first job as a social worker, at a veterans center in San Jose. Among her early clients, one stood out. “If you looked at him on the street, you’d think he had no skills, was just kind of bumming around,” Angell said. “But he was so bright, so capable, and yet he didn’t have a place to live. It took a couple of years of working with him until he thought he had earned or deserved a home.”

Today, Johnston, 54, and Angell, 59, are trying to find homes for every veteran in the country. Both hold leadership positions in their respective agencies — Johnston at the Department of Housing and Urban Development, Angell at the Department of Veterans Affairs.

For their unusual collaboration, and the results it has helped produce, Johnston, Angell and their staffs have been collectively nominated for a prestigious federal workers’ award, one of nine 2012 Samuel J. Heyman Service to America Medals, sometimes called “Sammies” or “government Oscars.” The nonprofit Partnership for Public Service, which administers the awards, will announce the winners in September.

The Johnston-Angell team is a finalist for the Citizen Services Medal. The two share the nomination with HUD’s Ann Oliva and Laure Rawson, and the VA’s Lisa Pape, Peter Dougherty, Vince Kane, Stephanie Robinson and Timothy Underwood.

According to HUD’s latest estimates, there are 636,000 homeless people in the United States, and more than 67,000 of them — 14 percent of homeless adults — are military veterans.

Just 10 years ago, most homeless veterans had served in Vietnam, the ongoing victims of a war long past. But a decade of conflict in Iraq and Afghanistan has made homelessness among veterans a fresh and urgent issue.

Recognizing this urgency, President Obama — who spent the day before his inauguration at a homeless shelter — has made a priority of reducing homelessness in general and ending veteran homelessness. These tasks fell to HUD Secretary Shaun Donovan and VA Secretary Eric K. Shinseki, who announced in 2009 an ambitious plan to end veteran homelessness by 2015. Johnston and Angell were tapped to lead the effort.

“We come to the mission with different expertise and assets,” Angell said recently. “They have the housing, and we have the clinical care. So when we put the two together, that really is the best way that we’re going to end homelessness.”

They’re a long way from that goal, but among veterans, the team has made significant inroads. In 2010, HUD and VA reconciled their survey methods and began conducting a joint annual homelessness census to establish a consistent measure by which to judge their efforts. Between the 2010 and 2011 surveys, veteran homelessness dropped by 12 percent. The 2012 results will be released soon and are expected to show a similar drop.

That decline can be partly attributed to the HUD-VA Supportive Housing Program, often called HUD-VASH, through which homeless veterans are supplied with Section-8 housing vouchers. HUD-VASH has existed since 1992, but in recent years the program has grown significantly. Until 2008, HUD-VASH could offer just 1,800 vouchers. Today, the program is in the process of distributing 48,000 vouchers, with 10,000 more on the verge of approval in Congress.

With $1.5 billion from the 2009 American Recovery and Reinvestment Act, HUD also started a Homelessness Prevention and Rapid Re-Housing Program, which is designed to help keep its clients from relapsing into homelessness after an initial burst of government support. The VA has modeled its own veteran-specific Supportive Services for Veterans Families program after the success of HUD’s HPRP.

The joint initiative has developed its own military vernacular. When Johnston’s staff at HUD compares notes with field workers and local officials, they do so at a “boot camp.” And one of the VA’s most visible outreach events is a series of “Stand Downs” at which homeless veterans receive services from legal advice to haircuts.

Angell, Pape and Dougherty recently attended a Stand Down in San Diego, which marked the 25th anniversary of the first such event. Angell, for her part, volunteered at a kiosk distributing free clothing. “Even at this level,” she said proudly, “you do have those opportunities where you can directly serve a homeless veteran.”

Angell, whose father and uncles served in the Army, Navy and Marines, has settled in Arlington after many years spent bouncing among Hawaii, Florida, Arizona and her native California.

After her first close encounter with homeless veterans as a social worker in San Jose, Angell earned a doctorate in marital and family therapy and moved back and forth between California and Hawaii managing a growing number of veterans’ health facilities throughout the Pacific coast and islands. In 2000, she advanced to a series of associate directorships that took her to St. Petersburg, Fla., and Long Beach, Calif.. She then spent three and a half years directing a medical center in Prescott, Ariz., before taking on her position in Washington.

Johnston grew up in Salt Lake City, where he was an Eagle Scout as a youth. Today he lives in Fredericksburg with his wife and five children.

After completing his assignment at the White House in the 1980s, Johnston returned to the USDA just as the department was looking to join the fight against homelessness. “I was the new guy on the block,” Johnston said. “They said, ‘Well, there’s this temporary issue called homelessness, and you’re the Agriculture Department lead. Good luck with that.’ ”

From that early effort Johnston moved to the U.S. Interagency Council on Homelessness. He transferred to HUD in 1990.

Although Obama has injected anti-homelessness efforts with fresh energy and resources, VA’s Dougherty said his colleagues’ campaign is not dependent on any one administration.

“Every secretary that’s been here has had an interest and a desire to help veterans who are homeless, and to help their homelessness end,” he said. “The difference is that we now have a momentum that has occurred that is almost an unstoppable force.”