Cliff says 'Seattle Center was one of 22-26 large air control centers at the time in the US. Seattle Center was in a building below the tower at SEA-TAC.'
According to websites this was during the 50's and a new location was built in 1962 where the Seattle center is today. I don't know enough to confirm these dates though. the information comes from there site..
TRACON controllers might of been there. that's the approach guys. (terminal radar approach control)
The original Seattle Air Route Traffic Control Center was located at the Boeing Field
Administration Building in 1940 and control instructions were relayed to pilots via company phone
lines.
In 1950, Seattle ARTCC moved to the Seattle Tacoma Airport (SeaTac) Administration
Building, where the first radio was commissioned in the facility allowing direct controller to pilot
communications.
In 1962 the ARTCC moved from SeaTac to its current location in Auburn,
Washington. The new, larger building allowed for further expansion and new equipment.