Here’s a neat automotive accessory from days gone by: the evaporative air conditioner, better known as the swamp cooler.

Today, more than 99 percent of the passenger vehicles sold in the United States are equipped with air conditioning, but in historical terms, we might regard that as a recent  development. In 1940, Packard was the first carmaker to offer A/C in a production car (see our feature here) and the industry eventually followed, but the feature was expensive, costly to maintain, and took decades to catch on with car buyers. As a factory option, air conditioning didn’t reach 50 percent market penetration until 1969. For many drivers, especially in hotter climates, there was a less effective but less expensive alternative: evaporative air conditioners, more popularly known as swamp coolers.

The most common type of cooler hung on the passenger door, using the vehicle’s airspeed (sometimes aided by a small electric fan) to force fresh air into the cabin. Inside, a water tank saturated a section of foam or woven fabric. As air traveled through the element, the water droplets absorbed some of the heat, sending cooler air into the cabin and offering some relief. Since the evaporative effect is greater in dry air than in humid air, desert cooler might be a better name, but swamp cooler stuck with consumers. While while it’s not as effective as refrigerant-based A/C systems, naturally, it does work and it makes a difference, especially on the hottest days.

Sears, Western Auto, Firestone, JC Whitney (above) and other mass merchandisers sold coolers, and a few enterprising outfits rented them to tourists passing through the desert. Along with the window-mounted coolers, there were larger under-dash units, and even elaborate trunk-mounted evaporative coolers (below) that mimicked the early factory refrigerant A/C systems offered by Packard, Cadillac, and others.

Today, a number of companies offer restored, reproduction, and modern-design swamp coolers for vintage car enthusiasts seeking both summer comfort and period authenticity. They may not function quite as effectively as refrigerant air conditioning, but they do look pretty cool.