icebox

As the techniques for food preservation steadily improved, prices decreased and food became more readily available. As more households adopted the icebox, the overall quality and freshness of this food was also improved. Iceboxes meant that people were able to go to the market less and could more safely store leftovers. All of this contributed to the improvement of the population's health by increasing the fresh food readily able to be consumed and the overall safety of that food. However, with metropolitan growth, many sources of natural ice became contaminated from industrial pollution or sewer runoff. Thanks to the icebox manufacturing industry's efforts, a new innovative idea in cooling came about: air circulation. The idea for air circulation in refrigeration systems stems back to John Schooley, who wrote about his process in the 1856 Scientific American, a popular science magazine. Schooley described the process as "Combining an ice receptacle with the interior of a refrigerator … a continuous circulation of air shall be kept up through the ice in said receptacle and through the interior of the refrigerator … so that the circulation air shall deposit its moisture on the ice every time it passes through it, and be dried and cooled." This idea of air circulation and cold led to the eventual invention of the mechanical, gas-driven refrigerators. As these early mechanical refrigerators became available, they were installed at large industrial plants producing ice for home delivery. By the early 1930s, mechanical ice machines gradually began to rise over the ice harvesting industry thanks to its ability to produce clean, sanitary ice independently and year-round. Over time, as the mechanical ice machines became smaller, cheaper, and more efficient, they easily replaced the hassle of getting ice from a source. For example, the De La Vergne Machine Company (originally called the De La Vergne Refrigerating Machine Company) of New York could produce up to 220 tons of ice in a single day, from a single machine. With widespread electrification and safer refrigerants, mechanical refrigeration in the home became possible. With the development of chlorofluorocarbons (along with the succeeding hydrochlorofluorocarbons and hydrofluorocarbons), that came to replace the use of toxic ammonia gas, the refrigerator replaced the icebox, though icebox is still occasionally used today to refer to mechanical refrigerators.

Underground pits with the constant underground temperature of 54 F had been used since Roman times to help preserve ice collected during winter. The temperature of the soil is held relatively constant year-round when taken below the frost line, located 3 to below the surface, and varies between 45 and depending on the region. Prior to the convenience of having refrigeration inside the home, cold storage systems would often be located underground in the form of a pit. These pits would be deep enough to provide insulation and also deter animals from the food within. Early examples used straw and sawdust compacted along the sides of ice for further insulation and slower melting. • Illustration — Women delivering ice. During WWI, many women were employed as icemen (or "ice girls", as they were called). By 1781, personal ice pits were becoming more advanced. The Robert Morris Ice House, located in Philadelphia, brought new refrigeration technologies to the forefront. This pit contained a drainage system for water runoff as well as the use of brick and mortar for its insulation. The octagonal pit, approximately in diameter and underground was able to store ice that obtained in winter until the next October or November. Ice blocks collected during winter could later be distributed to customers. As residential iceboxes appeared in the early to mid 19th century, ice collection and distribution expanded and soon became a global industry. During the latter half of the 19th century, natural ice became the second most important US export by value after cotton.