19th Century New York City, United States of America Living Conditions, Insects Propagating Disease, American Physician Stephen Smith’s Discovery of Typhus Epicenters, Human Excrement “Night Soil”, Various Methods Butchers Used to Retail Expired Meat Products, American Writer Upton Sinclair’s Shocking Expose of Food Preparation Conditions and the Development of the Food and Drug Administration as a Direct Result, The Infamous Mary “Typhoid Mary” Brown, Danish-American Journalist Jacob Riis’ Shocking Photography of Poverty During the 19th Century, Horse Manure Helping Push Development of Motorized Vehicles, the Reason Gasoline Powered Vehicles Supplanted Electric Vehicles, and American Mechanical and Chemical Engineer Thomas Midgley Jr.’s Idea to Add Lead to Gasoline to Make it Less Flammable and His Discovery of Chlorofluorocarbons Which Created the Hole in the Ozone Layer