"The parish of Stair is in the district of Kyle, lying on the south or right bank of the river Ayr, and extending six miles in length, by about two in breadth; it was first erected into an independant parish in 1653, when it was severed from Ochiltree for the accommodation of the noble family of Dalrymple, of Stair. The village of Stair, which comprises but a few dwellings and a neat parish church, is about two miles and a half from Torbolton; its situation is most romantic, and many highly ornamental mansions add tot he beauty of the surrounding country. The neighbourhood abounds with mines of coal. The earldom of Stair is now merged in that of Dumfries; and the principal heritors of the land, at the present day, are Lord Glencoe and Sir James Boswell."
Torbolton, Failford, Stair and Joppa - Ayrshire Directory - 1837 published by Pigot & Co.
Stair, which is well described in the quotation above, is a very small parish in the centre of the county, sandwiched between Coylton and Ochiltree. The current Stair Parish Church has its own web page.
An 1837 description of Torbolton (as it was then spelt), Failford, Stair and Joppa, including a listing of the key personalities, is given in this extract from Pigot's Directory for Ayrshire. The transcript was provided by Keith Muirhead from Queensland.
You can see pictures of Stair which are provided by: