St Mary's Parish was founded in 1847 with a chapel in the old Mechanics' Institute on the corner of Chapel St / Market St. Mount Pleasant, the land on which the Church is built, was purchased in 1851, the first building being erected in 1853. Changes have occurred. The present building dates around 1872, with the 8-peal Bell Tower added in 1894.
This was during a period when Chorley's population was growing rapidly, as the following figures show: 1801 = 4,516; 1851 = 12,684; 1901= 26,854. By 1901 it is estimated that c. 80,000 of this 26,854 people were Catholics, and this figure continued to grow.
St Mary's Church is often described as a "gem" of the Archdiocese of Liverpool. The edifice, in Early English style, has a polygonal chancel, nave, transepts, north and south porches, side chapels, and a north-east tower with corner turrets. The church is approached from three directions, from the North via Dole Lane or through the car park, from the South via West Street, or the original main approach from Market Street through the fine Archway opposite Chapel Street.
Entrance to the Church is now via the south-west porch, close to the Presbytery. Entering the narthex the three doors in the right lead in to the resource area and thence into the Church proper.