About 30 years ago. There are some refineries that Royal Dutch Shell has out in Northern California that were refit to meet the new gasoline blend requirements mandated about ten years ago. Likely some similar refits have been done in other refineries in the last 15 years.
I grew up in a refinery town and the unions had a regular beef about this topic.
But no new ones have been going up for decades.
Nobody wants them, but everybody needs them.