Truly inventive, Rousseau (1844-1910) was a customs agent and self-taught painter who never left France.
The exhibit was two years in the making, a fairly standard timeline for major undertakings but relatively short compared to the Tate Britain's exhibition of artist John Constable's "Six Footers" that took 25 years.
Officials declined to assign a price tag to the project but hinted at costs in the millions.
One of the first steps in creating an exhibition is moving the works of art, in this case 202 objects, including 49 Rousseau paintings.
While the real exhibit would take up 8,000 square feet (720 square meters) of space, the gallery's designers in Washington built dollhouse-scale models of every room that would be part of the exhibit, tweaking the angles and proportions, the AP reports.
These models allowed them to glance through doorways and imagine what each piece would look like on the walls. Using pushpins and miniature Rousseaus, statues and exhibition cases, the organizers moved walls and removed the framed models - as many times as they liked.
Eventually, the flow of the exhibit comes down to what planners see in their tabletop models.
Planners consider the condition of the paintings in deciding on placement. Glazed paintings have greater protection and are hung in high-traffic areas, just in case a visitor brushes against them, according to the AP.
The eventual design transformed the two-story space into a tunnel, with visitors exiting onto a third-floor landing. Although longer than planners would have liked, the alternative was worse - visitors doubling back and a pedestrian traffic jam in the final rooms housing Rousseau's dramatic jungle scenes.
While the designers figured out the space, new walls were constructed 10 miles (16 kilometers) away at the gallery's workshop in Landover, Maryland. When the previous exhibit moved out of the gallery, the staff moved in to latch the steel-framed gypsum wallboard into the 16-foot (5-meter) ceilings.