The Flint water crisis began in April 2014, when the city began drawing its water supply from the Flint River to, according to officials, save money. The shift was supposed to be temporary while the city waited to connect to a new water system. Immediately, many of Flint's 100,000 residents began to complain about the water's taste and smell and reported hair loss, rashes, nausea, and other issues. The initial shift to drawing water from the Flint River is certainly a key moment here as it is the beginning of what would become one of America's most serious water disasters.
A second key moment would be in September 2015, when doctors first began to report high levels of lead in people's blood, particularly children, and alerted city officials. State regulators, however, insisted that the water was safe. Just a few days later, then-Governor of Michigan Rick Snyder announced that the state would take action to address the problem, marking the first acknowledgement by the state that there was a major problem.
A third key moment could be January 2016, when Governor Snyder formally requested federal aid and a major disaster declaration from then-President Barack Obama. This marked not only Michigan state officials acknowledging that a crisis was underway and needed immediate help, but the involvement of federal officials in what would become one of the worst public health crises in US history.