Historical Notes By the mid 1950s there was no doubt among scientists that cars were a primary factor in LA’s smog crisis.

However, Los Angeles had no influence over the auto manufacturers. Smog wasn’t yet a national problem and it was very easy to dismiss smog as a quirk of LA geography.

Automakers were slow to respond. They were wary of any change that would add cost to their vehicles. As a result of public pressure, emission regulations would come to pass. But, it would take another two decades for things to change.

It wasn’t until 1975 that the U.S. required new cars to have catalytic converters, the key piece of technology that allowed everything to change. ^