The squat warehouse at Miami’s 5th Street Terminal was nearly obscured by merchandise: used car engines; tangles of coat hangers; bicycles bound together with cellophane; stacks of wheelbarrows; cases of Powerade and bottled water; a bag of sprouting onions atop a secondhand Whirlpool refrigerator; and, above all, mattresses—shrink-wrapped and bare, spotless and streaked with dust, heaped in every corner of the lot—twins, queens, kings. All this and more was bound for Port-de-Paix, a remote city in northwestern Haiti.

When I first arrived at the warehouse on a sunny morning last May, a dozen pickup trucks and U-Hauls were waiting…