In the Haitian capital of Port-au-Prince, the most crowded city in one of the most densely packed countries in the Western Hemisphere, class and elevation are inextricably linked. The city was founded on the coast, at the foot of the Chaîne de la Selle mountains, and over the centuries spread upward and outward from the sea. And as the city grew, so did its economic disparity. Now the coast is home to blighted sectors like La Saline and Cite Soleil, where some of Haiti’s poorest scrape together a living on streets that fill with trash after a heavy rain. Just above that is Delmas, a middle-class district of cinderblock houses and a main boulevard where pedestrians weave through perpetually gridlocked traffic. Above them all is Pétionville, where Haiti’s wealthiest citizens and foreign-aid contractors live amid upscale hotels and well-tended parks, with sprawling markets and grand villas that overlook the city and the sea.