From Wikipedia:
Completed in 1914, the 38-story, 484 ft (148 m) tower is the oldest skyscraper in the city and was the tallest office building west of the Mississippi River until the Kansas City Power & Light Building was built in 1931. It remained the tallest building on the West Coast until the Space Needle overtook it in 1962.
For decades, the Smith Tower's observation deck was a favorite vantage point. Check out these old post cards.
"Second Avenue in the business District, as seen from the top of the 42 Story L. C. Smith Building, Seattle, U. S. A."
#3,000 Published by C. P. Johnston Co., Seattle, U. S. A. Copyrighted 1913 by Frank H. Nowell. R-40703 C. T. American Art
"Looking up Second Ave. from Smith Tower, Seattle."
16126 Pub. by The Puget Sound News Co., Seattle, Wash
"Harbor and Second Ave. from Smith Building, Seattle, Washington"
#1756 Edward H. Mitchell, Publisher San Francisco
"Seattle Skyline. Viewed from the 42 story Smith Tower. Seattle's Financial district forms the foreground with the waterfront and uptown districts forming a background"
C-59 Ektachrome by Larrie Seifert. General Natural Color. Made by Dexter Press, Inc., West Nyack. N. Y. Pub. By J. Boyd Ellis, Arlington, Wash." It appears the Alaskan Way viaduct is under construction so I'd date this about 1953.
"Seattle, Washington. From Smith Tower's observation platform 35 stories high, is seen this view of busy Seattle, Washington's major city. On the left is a portion of Puget Sound and waterfront." Natural Color from Kodachrome. Mike Roberts Color Production Berkeley 2, California. Published by C. P. Johnston Co., Seattle C971. Postcard mailed June 1954
"Seattle, Washington. Looking North from Smith Observation Tower."
P3789. Plastichrome by Colourpicture Publishers, Inc., Boston 15, Mass., USA, Color by Roger Dudley. Pub. by Smith's Scenic Views, Tacoma, Washington
"Seattle, Washington - From Smith Tower's observation platform, 35 stories high, is seen this view of busy Seattle, Washington's major city. On the left is a portion of Puget Sound and waterfront. In center is new Norton Bldg."
Color photo by Max R. Jensen
"Seattle Skyline as viewed from atop the 42 story Smith Tower. The financial district is in the foreground while on the left may be seen the Alaskan Way viaduct which carries through traffic along the waterfront. Lake Union is on the far right."
Ektachrome by Clifford B. Ellis. Published by Ellis Post Card Co., Arlington, Washington 33275-B. C-59 Made by Dexter West Nyack, NY. I believe that black building that appears in this view is the Norton Building which was completed 1959 so I believe this postcard is between 1959-1962