The parish is in the northern part of the Penicuik and District Community Council area[2] and includes the village of Auchendinny near its eastern boundary.

[1][4] Historical records of the parish before 1878 spell it in various different ways - Glencors, Glencrosss, Glencrosse and Glencorse.

George Chalmers in his book "Caledonia" claims the name comes from "a very remarkable cross, which has been erected in the vale of Glencross by pious hands."

Yet another theory is that the name comes from a miraculous cross that appeared above Carnethy hill and encouraged the Scottish soldiers to defeat the English forces at the Battle of Roslin in 1303.

[6] The parish was originally named after St. Catherine, because of the chapel (St. Catherine-in-the-Hopes) dedicated to her which stood in the valley of Glencorse Burn (now submerged under a reservoir)[7] and is mentioned in a record dated 1230.

[9] The author Robert Louis Stevenson attended services in the church in his youth when he lived in Swanston village nearby and once described the Old Kirk as the "most delightful place on earth.

"[10] Stevenson's letters to his friends often mention the Old Kirk and he used his memories as models for the churches in his books "A Lowder Sabbath Morning," "Weir of Hermiston" and "The Body Snatcher.

The Old Kirk building acquired a new roof about 2004[11] and, in 2021, was rented out for weddings and events, having been superseded for parish use by a much larger church.

[5] The font was found in the floor of the Old Kirk during renovations in 1811 and is thought to have originally come from the Chapel of St Catherine, which was flooded during the creation of the Glencorse Reservoir.