From Teletraan I: The Transformers Wiki

The Seattle-Tacoma area is a location in the Generation 1 continuity family.

The Seattle-Tacoma area is a region on Earth. Presumably, it is related to something called Seattle and something called Tacoma.

In the real world, Seattle and Tacoma are two major cities in Washington State, and are the financial and military hub of the region.

[edit] Fiction

[edit] Generation 1

[edit] Animated continuity

When Megatron brought the Key to Vector Sigma to Earth, he began experimenting with it in an area identified by Teletraan I as "40 miles west of the Seattle-Tacoma area." The ensuing battle threatened a nearby city, though it's unlikely it was either Seattle or Tacoma, based on geography and proximity. The Key to Vector Sigma, Part 2

"40 miles west of the Seattle-Tacoma area" would be the Olympic National Park, which is consistent with the evergreen forest Megatron began cyberforming with the Key.