

A few reasons. One is there isn’t much flat land; most of it is hilly and even mountainous and covered in thick forests. The flat areas are occupied with farms and towns but the space is small and not enough for big cities to grow. The hills and mountains are heavily forested and there has never been a big enough population to need to encroach on them. It’s also not great for building and farming, unless grazing animals.
The other big reason is there are no natural deep sea ports in that region. It’s either marshy or the estuary of the river Colombia. Small fishing towns would be fine, but not big industrial ports that drive city growth (or did in the past). Meanwhile, Portland sits further back up the river with plenty of flat land and access to the water, so makes a natural port. And Seattle sits on the bay further north and is coastal, and a good port.
The dynamic got set up of big cities further back, and those areas never really grew. Once the land became part of state forests, then that restricts growth even more.
EDIT: Here is a topographical map showing in blue the flat land: https://en-gb.topographic-map.com/world/?center=38.54817%2C-119.79492&zoom=6





I wonder if the world will ever standardise to one or the other?
The . for decimal separator is used in English, as well as China and India but apparently that is only 35-40% of the global population. The , is used for 60-65%. Although the figures may not be accurate as a lot of countries seem to use both, with . used for international business, and internationally published science tends to be published in English?
Probably never be standardised as it’s probably too difficult to switch now? 1,000,000.00 and 1.000.000,00 are clear because of the use of three 0s for thousands etc, and two 0s for decimals. But 1.001 and 1,001 are much more ambiguous and would definitely need context as to which system is being used - is it 1 thousand and 1 or 1 and one thousandth?