In the film, it can kind of be seen when the young George, Harry, Marty, and Sam are sledding down the hill when Harry falls into the river. In a scene that was cut from the film, Potter watches the action occur from his mansion, and a no trespassing sign can be seen next to the river, marking Potter's property line.
The side of the box reads, "Built in 1889 at a cost of more that $250,000.00 the Potter mansion is the biggest and most imposing home in Bedford Falls. It is no accident that Mr. Potter chose a home that looked like a feudal castle. As the 'lord of Bedford Falls', Mr. Potter's home rules over all real estate in the community. As large as it is, nobody is ever seen visiting the old miser."