Glasgow to Penrith via M/A 74

There’s a world heritage centre at New Lanark https://www.newlanark.org/

Carlisle Castle https://www.english-heritage.org.uk/visit/places/carlisle-castle/

Tullie House Museum https://www.tulliehouse.co.uk/

Devils Porridge Museum https://www.devilsporridge.org.uk/

If you are into Anglo Saxon crosses https://en.wikipedia.org/wiki/Ruthwell_Cross rarely visited but incredible.

All of the above - especially New Lanark.

Moffat is also just off the M74, a pleasant market town.

I agree with the above. It’s a route that’s a bit lacking in things to see - most just drive quickly through. There are better examples of castles than Carlisle and Carlisle itself has few redeeming features.

I would head to Dumfries - see Sweetheart Abbey ruins, the Robert Burns Centre and Caerlaverock Castle is just south of Dumfries.

Very good chip shop in Moffat..

Not on route but not far off , Wanlockhead and the astonishing Buddist Temple at Eskdalemuir.
There's a stone circle on the edge of Eskdalemuir ,it's only 100 yds from the road
Dalveen Pass is also pretty impressive.

AS you near the border you will drive through the Debatable Lands. The history of the Scottish / English Border is very interesting with reiving going on back and forth across it. LIddesdale was the heart of it. Hermitage Castle which was one of the Scottish strongholds was to the east of your trip. They don't talk about border clans as much as they do about Border Families--Armstrongs, Johnsons, Elliots, Nixons, Irvines, Maxwells, Grahams. There is a wonderful book by George McDonald Fraser, Steel Bonnets and Graham Robb has a new book about his time exploring them. I recommend them both! And P.F. Chisholm has a mystery series set on the border on the English side in Elizabethan times that features Sir Robert Carey. They are great!

My grandmother grew up in Carlisle and Gamblesby near Penrith. When I visited the area my B&B hostess's father-in-law had been in school when my great grandfather was the schoolmaster! She set it up so that I met him and a small group of friends that had known my grandmother. And they were Armstrongs and Johnsons!!!

Pam

Thank you, so much, wonderful travelers, for these terrific suggestions. I really appreciate your taking the time to provide them! Let us hope and pray that Ukraine is able to see peace quickly, that they heal, and we can all travel safely.

Update: For anyone else looking at the suggestions made here, I have discovered that many of the Historic Scotland sites mentioned here (Sweetheart Abbey, Caerlaverock) are closed or have limited access for safety concerns. The Historic Scotland organization - https://www.historicenvironment.scot/ - is undertaking an assessment and repair of many of their sites.

Drumlanrig is just off of the A74(M) in Dumfriesshire, another place to visit is also Lockerbie.

Thanks for the additional suggestion, MC!