Stevenson's history includes an interesting footnote on what could have happened if Olympia had gotten its way. Instead of going straight through the old Tumwater historic neighborhood down by the former Budd Inlet waterfront, the Olympia city leaders wanted the highway through their city.
The proposed route was to loop the interestate through the town coming from the west through the Percival Creek canyon. Then, it would go through downtown in a tunnel under 10th or an elevated roadway over 7th.
So, the two options both included a highway at the foot of the capitol campus. Option one was a new tunnel. Option two was a viaduct running just south Sylvester Park.
This overlay of Olympia in 1941 with our current roads shows exactly why this was feasible. Even though the old Swantown Slough was filled for decades by this era, very little of the south end had been developed.
After finding a way through downtown, it would have been easy to route the interstate through the rest of town.
I also find it interesting that when this plan was seriously being considered (1952 through 1954), it was the early days of Capitol Lake. The city was advocating for a major interstate to loop through a place that they'd just spent more than a decade pushing to become a lake. Hardly fitting the Wilder and White vision of Capitol Lake creation, I'd say.
Of course, Capitol Lake then was hardly the park rimmed area it is now. In the 1950s, the first lake park was still ten years off. There was still a major rail yard on the south bank under the capitol and industrial buildings were still on other banks.
So, in the mind of the city leaders, in the early 1950s, the lake being the setting of a major downtown park was hardly in the plans.
Going through Tumwater ended up being cheaper, so the state highway commission chose that route. But, it wasn't because Olympia didn't want it.