Cows. The Midwest — including Michigan! — once had some of the worst malaria outbreaks in the country. Anopheles mosquitoes had always flourished in the damp lowlands around streams and melting snow, and when settlers came, some of them carried Plasmodium parasites that the mosquitoes spread widely. The settlers' farming practices made for even more stagnant water, and their sod and log houses were perfect habitat for biting pests. After farmers had exhausted the soil, they started raising cows rather than crops — and mosquitoes prefer to suck bovine blood even more than that of humans, helping break the malaria cycle. In the South and other parts of the country, larvicides, pesticides, better drainage, bug-proof housing, mechanized agriculture that replaced human labor, and fewer people living in lowlands helped eliminate malaria.
Oppressive, burdensome, over-reaching government regulations. People like to complain about the government, but when you start looking through the alphabet soup of agencies, you realize that most of them are there to save your life. The National Oceanic and Atmospheric Administration runs the National Weather Service and warns you about hurricanes. The Environmental Protection Agency enforces the Clean Air Act and has dramatically reduced the amount of deadly pollutants in the air you breathe. The Occupational Safety and Health Administration keeps you safe at work. The National Highway Traffic Safety Administration and National Transportation Safety Board investigate vehicles and accidents and make recommendations so accidents don't happen again. The Food and Drug Administration keeps deadly microbes out of your food. The Consumer Product Safety Commission recalls toys that could kill your child. The Centers for Disease Control and Prevention tracks and tries to cure or avert basically any health hazard, and the National Institutes of Health supports some of the most important biomedical research in the world.
Goodness. Philosopher Daniel Dennett had an epiphany after emergency surgery a few years ago. It wasn't a religious epiphany — instead of thanking God, he realized he should thank human goodness: