[5] St Mary's first home was at 33 Claypath with six students, before moving into Abbey House on Palace Green, then to 9 The college behind Durham Cathedral, which is now occupied by the Chorister School.

For several decades there had been debates about St Mary's continuing as a single-sex college within the university, and it had been originally mooted in the 1970s that it should go mixed.

St Mary's was the last of Durham's colleges to become entirely mixed when it took in both males and females at undergraduate level in 2005, ending over a hundred years of tradition.

Some members of the college felt so strongly against the proposed plans in 2000 that they protested, marching on the University Offices at Old Shire Hall.

The recently refurbished Shepherd wing of the Fergusson building is a segregated women's-only area for students who, for personal, religious or other reasons, would prefer single sex accommodation.

The chapel is located on the top floor of the North East wing and was designed by the ecclesiastical architect George Pace.

In addition to interiors and furniture produced by Thompson of Kilburn (the Mouseman), it now houses a sculpture of the Blessed Virgin Mary by acclaimed sculptor Fenwick Lawson, which was commissioned in 2005 by the college.The basement location of the Chapel prior to the 1960s now houses the JCR Bar which is managed by a Student Sabbatical Bars Steward.

In 2015, principal Simon Hackett opened the new Boughton Wing in Williamson building which was established to maintain this provision and provide women-only accommodation to those who require it.

[8] The college arms are blazoned as "Argent a Cross Formy Quadrate Gules a Chief Azure thereon a Durham Mitre Or between two Lilies proper."