It is a long-standing academic tradition for theses to be evaluated by more than one professor. The usual practice is a committee of three, including your thesis director. With the help of your director, you will need to identify at least two other people to be on your thesis committee. At least one of the two must be a professor from the History department; the other may be someone from History or another department, a member of the university's administrative or professional staff, or even an expert from outside IUP. You and your director may wish to decide on the composition of your committee right away, but you may, if you think it wise, delay a decision until you have a clearer idea about the nature of your thesis and what additional expertise you might need on your committee.
The amount of contact you have with these two additional "readers," as they are often called, will vary. Sometimes one of them is put on the committee to help you with a particular aspect of the work, and you will consult on that point. In other instances you may see very little of them until the end of the project when they read your thesis and sit as a panel for an oral examination.