The Seattle Metroplex goes from the Ft. Lewis and Puyallup districts in the south all the way up to the Everett district in the north. See the district layouts on the map inside the back cover of an old SR2 book, or the tiny dotted outline on p. 14 in New Seattle, or online at
Shadowland (hover your mouse over different sections, click on different sections).
If you have a current map of the city of Seattle it covers only a fraction of the Metroplex, not including Bellevue, Redmond, etc. A map of the current Puget Sound area will show the districts and major highways, but not the little streets. What has often worked well for us is a Puget Sound map for the major travel routes between districts, a downtown Seattle City map (for locating Renraku, Aztechnology, etc.), and the GM making up any streets, blocks, buildings needed anywhere else.