The last stop on the Missouri State Prison tour is the gas chamber where 39 men and one woman were put to death. Inside the building is a big white metal tank with a submarine-like door and two chairs inside. Prisoners entered via the door on the right, the crime victim's witnesses entered through the door on the left. Around the right side of the building is another door for family of the prisoner. And up on the roof is a tall, white smokestack to vent the gas when the execution was complete. Guards would bring the prisoner over ahead of time and put him or her into one of two tiny holding cells inside. This gave the witnesses time to enter without bumping into the prisoner outside, and gave the prisoner time to stare at the big white tank, just outside the holding cell.