CHARLOTTE, N.C. — She was a little girl of 9 or 10, staring out a window in the Lincolnton, N.C., cotton mill where she worked.

Lewis Hine — the father of American documentary photography — captured the haunting image of the too-young textile employee in 1908.

It became one of the historic pictures among more than 5,000 he made while working for the National Child Labor Committee, documenting abuses of child-labor laws in textiles and other industries.

Most of Hine’s caption information included names, but the Lincolnton girl was identified only as a “spinner” at Rhodes Manufacturing. A second photo of her in the same mill with an older girl and a woman also had no names....