Why is the place to purchase tickets called a "box office"?

Answer 1

The term "box office" originates from the early days of the theatre. Entry into cheaper sections of the performances cost a single coin, and this fee was collected in small, locked boxes with coin slots in the top. Upon the boxes being filled up, a runner would take the coin-filled box to a back room where it was counted and stored. Hence, the room associated with the financial aspects of the theatre became known as a box office.

Answer 2

I believe it has that name because the best seats at one time were the box seats. They were like balconies, but each one was private, and had an excellent view. Most of the time in the movies, when people go to an opera, they sit in a "box." Picture the curtained balconies, and ladies with opera glasses.
So, if you wanted seats at the opera, you purchased a box from the box office.

Answer 3

I always thought it was because the room was usually very small, and rather box-like. It could be, however, that once upon a time money was kept in a cash box. (It still is at garage sales, flea markets, etc.)