Abstract: A cargo trailer having a frame assembly with pivotally mounted wall structures or frames. The frame assembly can be collapsed into a compact shipping configuration wherein the wall structures are positioned substantially parallel with the floor structure of the trailer. Various parts of the cargo trailer can also be stowed in the collapsed frame assembly for shipment of the frame assembly and stored parts. After shipment of the cargo trailer, the wall structures are pivoted into their upright positions and the final assembly of the cargo trailer is completed. Exterior panels may be shipped together in a compact stack with the frame to the final assembly location where the panels are attached to the cargo trailer.