St. Mary’s mission in Newmarket began in 1840. The size of the parish swelled throughout the 1840s, especially during the years 1846 through 1848, when the Irish Potato Famine brought a huge influx of immigrants to the area. Most of them settled in the area known as “Irish” or “Paddy” Town- around Main Street, just north of Davis Drive in East Gwillimbury. Here they built small homes out of logs, with a window in the east and a door in the west, using fieldstone fireplaces for heat. Gardens and small orchards were planted and barns were built to raise livestock. The Irish dietary staples of cabbage and potatoes were replaced with wild berries and venison. They sold excess produce in the village. Though the men took up jobs as labourers in Newmarket and its surrounding areas, the Irish Catholics were ostracized in their small community- excluded from the public school system and not allowed to live in the village.

By 1872, the Catholics of Newmarket had outgrown the tiny building that was St. Mary’s (on today’s Ontario street) and were in need of a new place of worship. Then-parish priest, Father Patrick Joseph Keane thought that the best spot for the new building would be on the site of the existing cemetery (where St. John’s parking lot exists today). Parishioners opposed this idea, because it involved the disinterment of the bodies in the cemetery. Many families had not been able to afford headstones and they feared that the remains of some of their loved ones would be left behind. Intervention by Archbishop John J. Lynch decided that the church would, in fact, be built on the site of the cemetery as a new burying ground had been selected in Paddy Town, just beyond the public one.

By the turn of the century, the ghetto that was Paddy Town had disappeared, and Irish Catholics were clustered in the area surrounding the church and school- from Huron Street (Davis Drive) south to Queen Street and Main Street west to Niagara Street. The Irish Catholic community in Newmarket remained tightly knit and fiercely loyal throughout the first half of the twentieth century, with small numbers of English, Scottish and French settlers joining their congregation. (information copied from Here.)

You can see some of the old headstones set into the ground in the south east corner of the cemetery.