In the first photograph,the crowd outside the church seems to be waiting for something to come down the street. Children stand up front so they can see. Women, in the garb of the mid-1800s, shield themselves from the sun with umbrellas. White-gloved soldiers mill around. And a few people have climbed a tree for a better view.

In the second shot, some heads are bowed. Men have taken off their hats. And the blur of a large black object is disappearing along the street to the left of the frame. What the scene depicts, why it was photographed, or where, has been a mystery for decades, experts at the National Archives say. But a Maryland man has now offered the theory that the two photos are rare, long-forgotten images of Abraham Lincoln’s funeral procession in New York City.