The old photo albums were such a familiar part of the Woods family’s Adirondack camp that no one paid them much notice. But when the 21-year-old James T. Stever took a closer look at the nearly 1,000 rare photographs that his great-great-grandfather Harry Fowler Woods had taken a century ago, he saw them with fresh eyes.

The sepia-toned black-and-white pictures showed candid moments from a groundbreaking diplomatic mission to the Far East, which William Howard Taft and a large entourage of congressmen, senators, businessmen and others made in 1905 at the behest of President Theodore Roosevelt. Mr. Woods, an amateur photographer and businessman who was a friend of Taft’s from their native Cincinnati, captured the heady atmosphere of the three-month trip with the new hand-held cameras that had just come on the market.

When Mr. Stever came across the pictures in 2004, along with Mr. Woods’s neatly typed captions, he was unaware that they documented a pivotal time in America’s diplomatic past, a moment when the country was beginning to flex its imperialist muscles. But he quickly realized that the images were deteriorating.