For me, photos and maps help bring history alive. Following is the official state highways map published by the Washington State Bureau of Statistics and Immigration in 1915.
Aside from a rather odd name for a State Agency at the time, the map is pretty interesting. Just click on the map to enlarge. The route that we now know as I-90 and Snoqualmie Pass was then known as the Sunset Highway. Not only was the actual physical route over the pass somewhat different then, but most of the highway across the state was on "other roads open to travel" - meaning they were not state funded and were a bit "rough". Only the solid black lines were state funded improved highways. No Federal funding then with funding responsibilities of the state, county and cities perhaps as confused as they are today.
Another observation: What we now know as Hwy 410 and Chinook Pass was first called Naches Pass after the "path" maintained by Native American Salish tribes crossing back and forth between Yakima and Nisqually. Later, it became called McClellan Pass named after George B. McClellan who scouted the Cascade Mountains and helped establish a route capable of supporting wagon trains - barely. McClellan was known for his insubordination, clashing with Washington Territory Governor Isaac Stevens and even opposing Abraham Lincoln as a failed candidate for the presidency. However, he also became a Major General during the American Civil War and has a calvalry horse saddle designed by him named as the official "McClellan Saddle" in military manuals. Our region attracted some real characters and misfits - some of the them brilliant who also did some very good things. Others, like Stevens, not so good.