We use variation in weather to study the long-term effects of activism during the original Earth Day on attitudes, environmental outcomes, and children’s health. Unusually bad weather on April 22, 1970 is associated with weaker support for the environment 10 to 20 years later, particularly among those who were school aged in 1970. Bad weather on Earth Day is also associated with higher levels of carbon monoxide in the air and greater risk of congenital abnormalities in infants born in the following decades. These results identify benefits to volunteer activity that would be impossible to identify until years after the volunteering occurs. (JEL D64, D91, Q51, Q53, Q54)