“Each building has a few competing histories,” Mr. Gray wrote in his final column, on Dec. 26, 2014. “Mansions, for instance, were the domain not just of fancy people upstairs, but also of servants below — who were they? Where did they come from, and go? And what about the people who moved in when the old pile was broken into apartments? There are many stakeholders in a single structure, not just the Astors and Vanderbilts.”

Besides the columns and books that appeared under his name, Mr. Gray contributed to the overall scholarship of New York architecture through his Office for Metropolitan History. This was a research bureau for hire that he founded in 1975, when a building’s provenance could be learned only by poring over deeds, street atlases, directories, microfilm and old photographs.

Many of those documents were at his fingertips in a jampacked suite at Broadway and 80th Street, where the smell of 19th-century mildew mingled with the odors from a bagel bakery downstairs. Sometimes, the “office” consisted of Mr. Gray alone. But for many years, he was associated in his work with Suzanne Braley, Samantha Hightower, Melissa Braverman and his wife, Erin D. Gray.

His role was acknowledged in some of the more consequential books about New York buildings, including the “AIA Guide to New York City” and Robert A. M. Stern’s magisterial series: “New York 1880,” “New York 1900,” “New York 1930,” “New York 1960” and “New York 2000.”

“I came to rely on Chris as a significant resource,” Mr. Stern said on Monday. “He was generous with his time and always willing to share what seemed like his almost infinite knowledge of the city’s architectural and social history.”