Pendleton - Amazing wool shirts, and their cotton stuff is very solid. They still sell all-wool sweaters, which is becoming rare even at the high end. Sometimes eBay/poshmark have nice older USA-made pieces but sizing can be a crapshoot.
Brooks Brothers - Reliable for well-made warm-weather linens and cottons, pretty sure that remains so post-bankruptcy. Style choices run from 'Weekend Lawyer' to 'Insolent Schoolboy.'
American Giant - All-cotton tshirts and hoodies. Haven't tried their pants.
Woolrich - Good sweaters and heavy shirts. My first sweater from the now-shuttered PA factory has survived 30 years with spells of very rough traveling and outdoor work without holes.
Bemidji Woolen Mills - Wool Mackinaws and barn jackets do well in most situations where waterproofing isn't required.
Arc'teryx - The Canadian-made Gore-Tex stuff is very durable. Overseas-made no slouch either. I believe Gore is making serious progress in shedding fewer microplastics.
Double Pump - I think this is a captive Amazon brand? Durable and inexpensive cotton cowboy snap work shirts, the only ones I've found that are not synthetic blend. Ely Cattleman has a line of 97% cotton shirts but most are awfully rodeo-y.
LL Bean - Still make good casual and lined winter pants, but they're going downhill fast in nearly every other category. Will market something as 'wool' when it's 95% synthetic.
Eddie Bauer - See LL Bean, maybe with better shirt choices.
Smartwool/Meriwool - Base layers are magic, both brands seem indestructible. Smartwool socks are nice for all but the hottest weather. Meriwool is more likely to be all-wool. Runner-up goes to Peoplesocks brand.
Oh and the key to laundering all of these natural fabrics? Wash as cold delicates, dryer cycle with no heat for wrinkles, hang dry near a dehumidifier.