A cargo box for a vehicle includes a base member having a first edge portion, a second edge portion, a first side edge portion and an opposing second side edge portion. A first cross sill extends across the base member. A second cross sill extends across the base member. A side panel member is coupled to the base member along one of the first and second side edge portions. The side panel member includes an opening. A step assembly includes a first step support coupled to the first cross sill, a second step support coupled to the second cross sill and at least one step member coupled to and extending between the first step support and second step support. The step member is arranged at the opening in the side panel member. The step member is decoupled from the side panel member.