A 30-ton ammonia chiller at the St. Louis World’s Fair gave the public its first experience with comfort cooling.
In 1904, the St. Louis World’s Fair introduced Americans to modern marvels like hamburgers, hot dogs, ice cream cones, peanut butter, fax machines — and air conditioning.
Outside, temperatures soared, and cones melted. But the Missouri State Building was the place to beat the heat, where an ammonia cooling plant in the basement delivered chilled air to the building, circulating it upward to the auditorium through fans and ductwork. The official Fair handbook boasted that the system could “reduce the temperature in the building to 70° even when the mercury may be in the 90s outside.”
It was the world’s first artificially cooled public building.
To the American public, it must have felt like magic. Air conditioning was brand-new, invented barely two years prior, and still treated largely as a manufacturing process. Ice and Refrigeration Magazine reported that some visitors, unaware the building was artificially cooled, “were struck with wonder” at the sudden change in temperature.
The system was modest by today’s standards: a 30-ton plant supplying about 35,000 cfm of cooling. Yet its impact was profound. For fair-goers sweltering in Missouri heat, the experience wasn’t just relief — it was a glimpse of what buildings could become.
Boykin Air 