The ancient parish church, St. Kentigern's, 3 furlongs SE of the town, was granted by David I, as early as 1150-53. It continued to be used for some time after the Reformation, but seems to have fallen into a ruinous condition by 657, and in 1777 was finally superseded by the present church. Within the burgh stood the chapel of St. Nicholas, which existed at the beginning of the 13th century. Its very site is forgotten, but it is known to have served as a chapel of ease from 1590 till 1777. In the present yard of the Clydesdale Hotel stood an Observantine or Franciscan friary, which is said to have been founded by Robert Bruce in 1314.
The present parish church, in the middle of the town, without is a large ungainly structure of 1777, but within was greatly improved in 1870. It contains 1800 sittings. St. Leonards Church was built as a chapel of ease in 1867 and in 1873 was raised to quoad sacra status. Other places of worship are a Free church, Hope Street and Bloomgate U.P. churches, an Evangelical Unions chapel, Episcopalian Christ Church (1858), and St. Mary's Roman Catholic church.
The Presbytery of Lanark comprises the quoad civilia parishes of Carluke, Carmichael, Carnwath, Carstairs, Crawford, Crawfordjohn, Douglas, Lanark, Lesmahagow, Pettinain, and Wiston, the quoad sacra parishes of Forth, Leadhills and Lanark-St. Leonards, and the chapelries of Haywood, Carstairs Junction, and Kirkfieldbank. The Free Church has a presbytery of Lanark, with churches in Abington, Carluke, Carnwath, Crossford, Douglas, Douglas Water, Forth, Lanark, Law and Lesmahagoe. The United Presbyterian Church has a presbytery of Lanark, with 2 churches at Lanark, 2 at Biggar, and 8 at Bonkle, Braehead, Carluke, Carnwath, Crossford, Douglas, Lesmahagow, and Roberton.
Population of the Presbytery:- 1871 - 38,103; 1881 - 40,806.
Extract from Ordnance Gazetteer of Scotland, 1884