Northallerton

1791 population was 1960

16 miles south from Darlington
16 miles east from Richmond, and Keynings, seat of the Earl of Malzard.

Town on the Great North Road in North Yorkshire. Currently county town of North Yorkshire.
Where Prudence Youlgrave is living at the beginning of An Unlikely Countess.

The High Street was wide and about 1/2 mile long. That width remains today.

It was a major coaching town, so the high street would have been lined with coaching inns, though the site below says only 4.
I think that must be an error. This page lists current pubs, some of which are clearly old.
Best inn was The Golden Lion, which is still there, though heavily changed inside.
Cate Burgoyne stops there en route to Keynings as earl.
Fleece Inn
The Old Golden Lion, now gone
The Black Bull
The King's Head

Yards were narrow streets leading off the High Street which were owned by the property-holder on the High Street and usually named after them. There was Three Tuns Yard behind an inn, and Clapham Yard owned by someone called Clapham.

External link.