Hi Howard -
I've been thinking about Westport, Washington. I started my x-USA trip in 2016 there.
Never had been there before, but had always wanted to. It was magical.
It had everything, but was out-of-the-way, laid-back - almost like a 1970s beach town.
There's a historic Coast Guard Station and a lighthouse - a great harbor filled with fishing boats.
If you are lucky, on a clear afternoon you can see across Grays Harbor to the snow-capped Olympics.
Downtown, along the harbor, has little one-story shops and cafes - no mega commercial.
There are motels, a grocery, a library, a hardware store. And two nearby state parks.
Best of all - there's a 2-mile paved bike trail along the dunes at ocean's edge.
A memorable way to start a trip.
I've started/ended trips from Cape Flattery down to southern Oregon.
Neah Bay has a great museum and Shi Shi Beach.
Cape Disappointment has great views.
Astoria is easiest to get to with every amenity.
Tillamook is funky and fun. With a cheese factory and bike shops.
Coos Bay has the feel of an old fishing & lumber town.
But Westport has the entire package - plus two great routes inland.
It's one drawback is that it is somewhat tricky to get to.
But a combination of public train/bus routes will do it - albeit slowly.
FWIW - I know your topic title says, "Oregon to Maine". Heh-heh.
But if you are willing to start a little further north.
Two constraints on planning a start/finish on the coast in the Pac NW are:
1. Where are you going to cross the Cascades/Gorge?
2. How are you going to get thru I-5 population corridor?
Cascade Crossings -
WA 20 is stunning, but remote - with big climbs early on.
US 2 is beautiful, but has heavy traffic and iffy shoulders on the west side.
I-90 permits cycling - but why? Old US 10 is not continuous.
The Iron Horse Trail is unpaved - pretty smooth - but puts you in the Seattle metro.
WA 410 is the loveliest of all - but extremely narrow - and Chinook Pass opens late.
US 12 is hard to beat - fairly low traffic, services, and nice views of Mount Rainier.
There are a series of paved forest roads in S. Wash, but the route is complicated and remote.
WA 14 was on my first x-USA trip - but it has way too much traffic now.
I-84 - Why again?
The Old Columbia Highway is great but means the Portland metro and puts you onto WA 14 or I-84.
US 26 has nice shoulders and Mount Hood Views - but has really heavy traffic.
Paved forest roads via Timothy Lake are pretty darn nice - access via OR 224.
US 20 Santiam Pass - O.K. shoulders, but again, heavy traffic kills the buzz.
OR 242 - McKenzie Pass is a really sweet crossing, but not dependable for early June.
The I-5 Corridor -
Mount Vernon - Crossing from the San Juan Islands to WA 20 is pretty easy.
Seattle Metro - Great, bikeable city - but just not worth it on a tour.
Centralia/Chehalis - Very easy crossing from coastal routes into the Cascades.
Longview - Tough. WA 4 scenic, but narrow. I-5 riding south. Dangerous Columbia bridge.
Portland Metro - Again great, very bike friendly - but just not worth it on a tour.
Salem - Not too difficult, the Willamette ferry and state park are nice.
Corvallis - Definitely a bike friendly college town. Some high traffic sections with shoulders.
Eugene - Again, bike friendly college town, but bigger. Paved bike trails and mostly wide streets.
I like Westport because if combines the best of the coast, an easy I-5 traverse, and a great Cascade crossing.
Pic - Westport Harbor with Olympics in the Distance