On this google map it is at "C". I added a more scenic route between it and the Sinks Canyon area. Knowing the area I wouldn't be surprised if most of it was gravel.
from:US-26/US-287 to:US-26/US-287 to:Green River Lakes Rd to:Unknown road to:Emigrant Trail to:Lander Cutoff Rd to:Louis Lake Rd/WY-131 to:Nevin Circle to:Sinks Canyon Rd/WY-131 - Google Maps
Emigrant Trail is something I want to check out in the area. Saw it on the maps and got curious.
Union Pass as it is called, between US-26 and Pinedale, is all gravel and an easy road. Fall brings the hunters up there to the high country. It's also Grizzly country, so you know, be careful and stuff... Your shown route from Boulder to the Loop Road and Lander is also all dirt (except a few short miles on US-28), mostly sand, ie Big Sandy Recreation Area. Great route, very scenic views of the Windrivers....
Lots of other good suggestions in this thread including Beartooth Pass, Old Faithful Lodge, Jenny Lake & inspiration Point (although I would hike to the point first and then take the ferry back), soaking in the Boiling River, Goose Lake Trail in Cooke City and the possibility of snow in September.
Some OP questions I didn't see answered -
One pass gets you in both parks (annual passes are now $80). Expect long construction delays around Lizard Creek in Grand Teton NP. Also some construction delays between Mammoth and Norris in Yellowstone...
You must stay in a campground in Yellowstone. Depending on the crowds, I would pick one and basecamp there for your stay. Nothing worse than running into "campground full" signs at 4pm and not having a clue where you'll stay that night.
Sinks Canyon in Lander, is a great place to stay. I live a few miles down the road and take my kids up there for overnighters all the time. Make sure to see the "Sinks" and the "Rise" while you're there. The section of the Loop Road that starts in Sinks Canyon is under heavy construction this summer. They are allowing traffic through at certain times of the day, check the ranger station to see when if you want to do that trip. It is an awesome drive by the way. Lots of beautiful lakes up there.
My local's tip to you regarding travelling through the national parks - gas. Anytime you're under half a tank and you see a gas station, top off. The distances are misleading, the amount of fuel you'll use is often surprising and stations are really spread out. That and secure that campsite ASAP. Better to drive all the way back across the park to your site, than driving in circles looking for a site. Been there, done that, hated every minute of it.
Bogo said:
from:Grand Loop Rd/US-212 to:44.947455,-110.453497 to:Grand Loop Rd/US-212 - Google Maps
There is a one way gravel road from "A" to "C" on the linked map. This is along the Grand Loop Road from Mamoth to Tower. Zoom way in on the satellite image and you can plainly see it.
You talking about the Blacktail Plateau road? Haven't seen that one open on my last few trips. You're right, they close that one often. They did have Dunraven Pass open this year which was the first time I've been able to drive over that in several years.
Lots of good info in this thread. It's great to see so many people appreciate this little corner of the world. This corner of WY truly is a wonderland.
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