REMOVE

1. Nitrate negatives
2. negative
3. Walking.
4. National parks & reserves.
5. Library of Congress Prints a …

WHAT

1. National parks & reserves … (1)
2. Nitrate negatives (1)
3. Photographs (1)

WHO

1. Genthe, Arnold (1)
2. Library of Congress Print … (1)

WHEN

1. 1869-1942 (1)
2. 1903 (1)
3. 1906 (1)
4. between 1903 and 1906 (1)