It is odd that Samuel J. Battle, the first black officer in the New York Police Department, is not a larger part of our city’s lore. He was a giant man — 6-foot-3 and nearly 300 pounds — who more than 100 years ago led the integration of the department, then essentially an Irish-American enclave.

Mr. Battle’s arc from humble Southern roots through racist barriers in New York would be a familiar story, like the stories of other black pioneers. But he was largely forgotten until a veteran New York journalist followed a trail that led to a remarkable discovery.

On a summer day in 2009, Arthur Browne, a broad and thick-handed man himself with closely cut silver hair, was reading his newspaper when he came across an article that surprised him. The city was naming a Harlem intersection after Mr. Battle, whom the article called “the Jackie Robinson of the N.Y.P.D.” Mr. Browne, who had expertly covered the city in one way or another for 40 years, realized that he had never thought about how the Police Department was first integrated.

“It struck me as a lapse because there was so much controversy through the years about the Police Department’s relationship with the black community, and over the number of African-Americans on the force,” he said recently in his office at The Daily News, where he is now the editorial page editor. “It just struck me that I never thought about how it all began.” So he started digging.