This house on University Terrace NW was designed by William Nixon, who from 1942 to 1962 was president of the Association of Oldest Inhabitants (Colored) Inc. (Bill Brown/Association of Oldest Inhabitants)

The answer to a question that has bedeviled some Washington history lovers for years finally came in an unexpected place: in front of a handsome art deco-style house in Northwest Washington. The question was: What’s the story behind the Association of Oldest Inhabitants (Colored) Inc.?

The group of leading black District citizens — founded in 1914 — was modeled on the Association of Oldest Inhabitants (AOI), a white group that was founded in 1865 and is probably the oldest civic organization in the city. As was the norm in those racially segregated days, the two groups were separate, but they occasionally came together for common ends. In 1919, they held a joint meeting to commemorate District residents — black and white — who served in World War I.

Two years ago, Nelson Rimensnyder, historian for AOI, made a plea in my column for information on AOI (Colored). He knew the group had existed and felt certain someone out there must have documents related to it.

And then James M. Goode stood in front of 2915 University Terr. NW, in Washington’s University Park neighborhood. James is a historian, the author of such must-have D.C. reference works as “Washington Sculpture” and “Best Addresses.” He’s working on a book about historic houses in Washington, and the University Terrace house will be in it. It’s a gem: Light-colored brick is arranged in curved sections, and one round exterior wall is clad in glass block.

The 1951 house was designed by a man named William D. Nixon, and when James spoke with the current owners, he learned that one of Nixon’s granddaughters lives in Silver Spring.

William Nixon was the president of the Association of Oldest Inhabitants (Colored) Inc. The D.C. high school art teacher was active in the civil rights movement in Washington (Family photo)

And so he went to meet that granddaughter, Delores Mounsey, who grew up in the University Terrace house. Nixon designed it for his daughter Ethel (Delores’s mother), a psychiatrist at Johns Hopkins Hospital.

As James flipped through family scrapbooks looking for information on the house, he found something else: page after page relating to Nixon’s involvement with AOI (Colored). Nixon was president of the organization from 1942 until shortly before his death at age 91 in 1962.

“It was really extraordinary,” James said of his serendipitous discovery.

Delores has donated three scrapbooks to the Moorland-Spingarn Research Center at Howard University.

“It’s really a snapshot of black upper-middle-class life during this time period in Washington, D.C.,” said Ida Jones, curator in the center’s manuscript division. “It will be a nice planet in our universe.

William Nixon was an interesting man. He was born in 1871 and graduated from D.C.’s Miner Normal School in 1891. He never attended a four-year college. It’s unclear how he developed his design skill — whether it was something he was born with or something he learned — but Nixon eventually became an art teacher in District public high schools, retiring as co-director of art at Dunbar.

He put his artistic skills to use in all manner of media. He designed the packaging for a patent medicine called Harris’ New Blood Tonic. (The logo showed a rabbit jumping through a hoop, an illustration, perhaps, of how rejuvenating the tonic was.) He painted landscapes and designed stage sets. He arranged tableaus, those ornate, living recreations of classical scenes so beloved in the 1920s. He hand-carved at least one piece of furniture. (Delores has the intricately detailed wooden chair.) And he designed three houses and a commercial building.

Granddaughter Delores Mounsey had preserved William Nixon’s scrapbooks. (John Kelly/WASHINGTON POST)

Of his sinuous University Terrace house, Delores remembered her grandfather saying, “Anybody can draw a straight line.”

Nixon used his position with AOI to fight for the integration of the District’s police and fire departments. His obituary in the Afro-American noted that he took a personal interest in the case of Carl and Anne Braden , a white activist couple who were charged with sedition for helping a black family buy a home in a segregated Louisville neighborhood. Nixon helped raise funds for the Bradens’ defense.

Bill Brown, president of today’s AOI, is delighted that Nixon’s scrapbooks will be available for research. “Our point always was, this stuff has got to be out there someplace,” he said. “Let’s have it not end up in the dumpster of history.”

There was never any danger of that, Delores said. “I kept my grandfather’s scrapbooks because he put them together,” she said, “and it was our family.”

What history is in your family’s scrapbooks?