Up until the Iranian Revalution, most of the worlds supply was grown in Iran, and we cut off trade with them.
In the US the growers began replacing the Almond Trees around Quartz Hill, Lancaster, and Bakersfield with Pistachios,
since they were losing their Almond trees to an unstoppable
Almond Blight which was slowly killing off the trees.
Pistachios are either resistant or not affected by the Almond Blight, and they are now raised in that area of Southern California,
second only to Iran in the world supply - we still don't deal with Iran for our imports.
It takes 7 to 8 years from planting before a tree bears a viable quantity of nuts for harvest.