In the absence of capable government services, a railroad company in Texas and multiple cotton mills in North Carolina successfully prevented malaria in the early twentieth century. This Article looks through the lens of economics to understand how and why people had the incentive to privately coordinate malaria prevention during this time, but not after. These firms, motivated by increases in productivity and profit, implemented extensive anti-malaria programs and used their hierarchical organizational structures to monitor performance. The factors underlying the decline of private prevention include a fall in the overall rate of malaria, the increasing presence of the federal government, and technological innovations that lowered exposure to mosquitoes. Understanding how, why, and when firms can prevent diseases has important implications for current disease policy, especially where governments, international organizations, and technologies are not enough.