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. Otto apparently printed it on contract for Central News Co. It was also printed as Image X70, as seen below:
There are multiple images numbered 7:
Reuse of image numbers and different image series make it difficult to know how many images Otto published.