Whitney Smith, who turned a childhood fascination with flags into a scholarly discipline — vexillology — of which he was the leading light, died on Thursday in Peabody, Mass. He was 76.

The cause was advanced Alzheimer’s disease, his son Austin said.

Mr. Smith, the author of the standard work “Flags Through the Ages and Across the World” (1975), became obsessed with flags around the time he started kindergarten, his enthusiasm amplified by the heritage of his hometown, Lexington, Mass., and its annual displays on the town green.

“When I was 8 or so, I’d go down there before Patriots’ Day and tell the highway department crew how to set up the flags in the proper order of admission to the Union,” he told Smithsonian magazine in 1997. “The workers always looked as if they wished this kid would go home to his sandbox.”

While other boys were memorizing baseball statistics, he amassed newspaper clippings and articles on flags and wrote to obscure foreign consulates asking for precise information on colors, stripes and symbols.