This photo was taken during construction of the grounds for the 1909 World's Fair held in Seattle, the Alaska Yukon Pacific Exposition. It was taken by the official photographer, Frank Nowell, whose logo is visible in the lower left. Otto apparently printed it on contract for the American Post Card Co.
A slightly different version of the scene was printed for the Central News Co. Frank Nowell probably took this picture as well.
There are also several versions of Image 46 (46 - Washington Timber) showing forests and an Image 46 (46 - Parad Golden Potlatch Seattle) showing a float in one of the Golden Potlatch festivals. Reuse of image numbers and different image series make it difficult to know how many images Otto published.