Read this excerpt from The Great Fire.

Schaffer's first signal went out at 9:30. Several minutes later, Schaffer realized his mistake and ordered Box 319 struck. This was still seven blocks away from the O'Learys', but close enough that firefighters could see the flames and alter their course. Unfortunately, Schaffer's young assistant, William J. Brown, stubbornly refused to strike Box 319, saying he was afraid it would confuse the situation. Brown was so stubborn about his decision that even after the fire he was able to write arrogantly in a letter that "I am still standing the watch that burned Chicago."

What caused the fire engines to head toward the wrong location?

The fire was too small for them to see.
Several fires were burning at once.
Schaffer’s assistant refused to correct the signal.
Schaffer and his assistant struck multiple boxes.