The headwaters of the river rise south of Mount Angelo, approximately 25 km south of Halls Creek.

The river then flows in a westerly direction through Oollumarra Soak and discharges into Margaret River, of which it is a tributary.

The river was named in 1884 when the area was explored by a government survey party led by Harry Johnston, who named it after his mother, Mary Johnston (1822–1893), a daughter of Marshall Waller Clifton and Elinor Bell.

The traditional owners of the areas around the river are the Djaru and Konejandi peoples.

This article related to a river in Western Australia is a stub.