A County Mile

We all know the expression A Country Mile. 
It refers to a distance which is greater than expected.
I have always thought it a confection to confuse town-dwellers and  found it particularly efficacious employed as such.  However there are academics who have more academic explanations and  adduce such literary references as:
Frederick de Kruger's The Villager's Tale (1829)

The travelling stage had set me down
Within a mile of yon church-town;
'T was long indeed, a country mile.
But well I knew each field or style;

Or:

The Treasury of Knowledge and Library of Reference  (1850)

Robin Hood shot a full mile; and, according to his bard, a north-country mile was equal to two statute ones.

I leave you to come to your own conclusion regarding its etymology as I believe I have identified a new measure - the County Mile, or rather the Lancashire Mile
This is smaller than the statute mile and so leads to inflation of distances. I cite two instances only, (but am sure there are many others):  both from the Leeds & Liverpool Canal.

Burnley's Straight Mile

The canal  embankment in Burnley is known as The Straight Mile

It would be churlish of me to dispute the straight description, but 1225 yards was never a mile in my books.

A few statute miles away, or, indeed, a country mile away, is the Foulridge Tunnel, known locally as the Mile-Long Tunnel. 
It is, in fact, 1640 yards long.
I cannot, or rather, do not dare to, suggest a reason for this phenomenon but offer it up for consideration.