[2] The medieval shire or sheriffdom of Cromarty encompassed a single tract on the north of the Black Isle peninsula.

[2] As late as the mid-nineteenth century, the boundary between Ross-shire and Cromartyshire was uncertain on the moor of Millbuie (in the centre of the Black Isle).

[2][3] Cromartyshire originally bordered Inverness-shire, but in 1504 an act of parliament purported to create the county of Ross-shire covering the rest of the old province of Ross.

It was not until a subsequent act in 1661 and the appointment of the first permanent sheriff of Ross in 1662 that Ross-shire properly functioned as a shire.

[7] The feudal barony of Cromarty, whose appurtenant land was coterminous with the county, was purchased from the Urquharts in 1682 by the Mackenzies of Tarbat.

[8] They owned scattered lands in Ross-shire, including the barony of Tarbat on the Moray Firth north of the Black Isle.

[8] In 1685 Sir George Mackenzie, recently made Viscount of Tarbat and later elevated to Earl of Cromartie, secured two Acts of the Parliament of Scotland transferring his lands in Easter Ross from Ross-shire to Cromartyshire.

[20] The Scottish Reform Act 1832 merged Cromartyshire's constituency with Ross-shire's to form Ross and Cromarty, returning one MP to Parliament.

They retained separate Commissioners of Supply, and from 1794 each appointed their own lord-lieutenants, with Cromartyshire overseen by the Lord Lieutenant of Cromarty.

[28][29] Download coordinates as: The 1881 index to the Ordnance Survey's first edition lists 22 detached parts, and the original "old shire", all of whose areas are given on the six-inch map.