St Mary's was built to accommodate the increasing population of the town in the early 19th century.

[1] The church was designed by John Latham,[a] and was extended in a matching style with the addition of transepts and a chancel in 1852–56 by E. H.

[4] The church was declared redundant by the diocese of Blackburn on 1 March 1996,[5] and was converted into a conservation centre for the Museum of Lancashire in 2006.

Both have round-headed doorways with a window above, and clasping pilasters, the outer one surmounted by squat pinnacles.

The transepts also have clasping pilasters, and at the corners these rise to two-stage turrets containing blind arcading and topped by pyramidal caps.

[8] Hartwell and Pevsner in the Buildings of England series comment that the outline of the church "seems to owe a debt to the pinnacles at the west end of Tewkesbury Abbey" and that the massing of the architectural details is "reminiscent" of works by Christopher Wren and Nicholas Hawksmoor.