Apparently they just changed what used to be a 250,000:1 inset on the Seattle sectional, to a separate Portland TAC publication. It looks like the new chart covers more area, about 50 nm wide, double the size of the old inset.
There are also three new north-south VFR transition routes published -- "Timbers" at or below 2500' from SV Highway down to 7S3; "Blazers" at or above 3500' from W52 to Oregon City; and "Thorns" at or below 4500' from the Larch Mountain prison to Crown Point to Sandy, then at or below 2500' to 5S9.
I imagine there's more information about these transition routes on the back of the chart, but the new chart isn't yet listed for download on the
FAA digital chart page.