On this day in 1980, 13-year-old Cari Lightner of Fair Oaks, California, is walking along a quiet road on her way to a church carnival when a car swerves out of control, striking and killing her. Cari’s tragic death compelled her mother, Candy Lightner, to found the organization Mothers Against Drunk Driving (MADD), which would grow into one of the country’s most influential non-profit organizations.

When police arrested Clarence Busch, the driver who hit Cari, they found that he had a record of arrests for intoxication, and had in fact been arrested on another hit-and-run drunk-driving charge less than a week earlier. Candy Lightner learned from a policeman that drunk driving was rarely prosecuted harshly, and that Busch was unlikely to spend significant time behind bars. Furious, Lightner decided to take action against what she later called “the only socially accepted form of homicide.” MADD was the result. (Charged with vehicular homicide, Busch did eventually serve 21 months in jail.)

In 1980–the year Cari Lightner died–some 27,000 alcohol-related traffic fatalities occurred in the United States, including 2,500 in California alone. After founding MADD, Lightner began lobbying California’s governor, Jerry Brown, to set up a state task force to investigate drunk driving. Brown eventually agreed, making her the task force’s first member. In 1981, California passed a law imposing minimum fines of $375 for drunk drivers and mandatory imprisonment of up to four years for repeat offenders. President Ronald Reagan soon asked Lightner to serve on the National Commission on Drunk Driving, which recommended raising the minimum drinking age to 21 and revoking the licenses of those arrested for drunk driving. In July 1984, she stood next to Reagan as he signed a law reducing federal highway grants to any state that failed to raise its drinking age to 21 (a change that was estimated to save around 800 traffic deaths annually); by the following year, all 50 states had tightened their drunk-driving laws.

MADD had expanded to some 320 chapters and 600,000 volunteers and donors nationwide by 1985, when Lightner parted ways with the organization. MADD went on to wage a campaign to lower the nation’s legal blood alcohol content from 0.1 percent to 0.08. The group won a major victory in 2000, when the Clinton administration passed a law tying federal highway funds to states’ adoption of the 0.08 standard. By that year–the 20th anniversary of MADD’s founding–alcohol-related fatalities had dropped some 40 percent over two decades, and states with the toughest drunk-driving laws were beginning to treat alcohol-related fatalities as murder.