At the end of the 19th century, Motherwell was growing with the development of local industry. The Church of Scotland saw that there was a need to extend its ministry among the growing population in the Watsonville area of the town. The first meeting place was a converted house in a miners' row. Under the care of Rev William Smith, the congregation quickly grew and in 1902 moved to a larger building seating 240. This was the Tin Kirk, so called because it was made of corrugated metal.
With further growth in the membership of this young church, it was clear that a larger building was required. A site in Avon Street was found. Both the existing congregation and residents of homes around the new building could easily walk to worship. This fine new church was opened in December 1914. It had taken a year to build at a cost of £4,333. Four years later, St Mary's became a full Parish Church in its own right.
Although the church itself was large enough to cope with the increasing membership of the congregation, there was a lack of accommodation for mid-week activities, which included Guild, Male Voice Choir, Guides and Boys' Brigade, so in 1955 a hall was built. Continuing growth in numbers made it necessary to enlarge the premises again and in 1969 a hall, a conference room and a coffee bar were added. A glance at the range of weekly activities will show that the halls are busy all day and all week.
Music is an important part of worship in St Mary's. In 2007, the pipe organ installed in 1951 was replaced with an Allen digital organ.
As St Mary's moves forward from its centenary it is a busy congregation in Hamilton Presbytery, set at the heart of a residential area of Motherwell. We can look back at changes that have taken place. The traditional industries of coal and steel, whose growth was the trigger for the birth of St Mary's, have largely gone. New housing within the parish has increased the number of homes to 1700. Within these changes a constant remains: St Mary's at the heart of the community, Christian worship Sunday by Sunday, Christian life day by day.