It covers Dumfries and Galloway, Ayrshire, Lanarkshire (including Glasgow), Dunbartonshire, Renfrewshire and west Stirlingshire (south of the River Forth).

The Diocese of Galloway (also known as Candida Casa or Whithorn) is thought to have been founded by Saint Ninian in the 5th century.

However, the small Scottish Episcopal Church continued the line of bishops of both diocese, even though, in the 16th century, many of them held the office in title alone.

Within a year, Drummond gave way to John Strachan as the newly appointed Bishop of Brechin, and, in 1805, resigned from the united see of Edinburgh and Galloway (to Daniel Sandford) to focus on ministry in Glasgow.

The diocese covers the historic counties of Dunbartonshire, Renfrewshire, Lanarkshire, Ayrshire, Wigtownshire, Kirkcudbrightshire, Dumfriesshire and western Stirlingshire.