This photo appears to have been taken during construction of the grounds of the 1909 World's Fair in Seattle, the Alaska Yukon Pacific Exposition. In that case it would be a Frank Nowell photograph; only Nowell and his staff were allowed to take photos during construction.
A different image with the same number was printed for Central News Co. It is probably a Frank Nowell photograph as well.
There are two other photos with image number 4:
We don't know which photos were taken first. Reuse of image numbers and different image series make it difficult to know how many images Otto published.