She is sorted into Gryffindor, although the Sorting Hat takes a long time to decide into which house, Gryffindor or Ravenclaw, she should be placed. After more than five minutes of deliberation, the Hat places her in Gryffindor (JKR, Pm).
Minerva McGonagall starts at Hogwarts
Certainty Stated in canon
Location in Canon Pm
Type of Event Wizarding world