A stackable container has a bottom panel, upstanding sidewalls, upstanding end walls, and an open top. According to one aspect of the invention, narrow reinforcing flaps are attached to the upper edge of at least one of the side and end walls, defining a stacking ledge and reinforcing the walls against outward bulge. The reinforcing flaps extend over only a small portion of the height of the side or end wall, and corner post flaps extend from opposite ends of the reinforcing flaps, extending diagonally across interior corners of the container. According to another aspect, the side and/or end walls lean inwardly, defining a narrower footprint at the top of the container than at the bottom. In a specific embodiment one of the walls leans in more than the other. According to a further aspect, an indexing and aligning tab extends upwardly from an upper edge of the container, and a complementary notch is formed in a lower edge for receiving the tab when the containers are stacked. According to a still further aspect, stacking tabs extend upwardly from the upper edge of the container, and slots are formed in the bottom panel for receiving the tabs when containers are stacked. Locking flaps extend into the slots to frictionally engage and hold the tabs.