There are about 3400 ha of date palm in the Coachella Valley, a Southern California desert. Here is a road side view (note how you can you can estimate the growth rate by comparing with the 2007 street view photo) and here is another grove. Wikipedia says that that the Spanish introduced the date palm to lower California (Mexico) in 1765; but Walter Swingle gets the credit for bringing the plant to the USA (see this letter by David Fairchild). In 1903 he collected Deglet Noor in Biskra, Algeria, and in 1929 he collected the prized cultivar Medjool in Morocco.
Coachella date grower Patricia Laughlin has this to say about that:
When the Medjool dates came in, there were only nine offshoots that all of the present trees come from. These medjools came from the oasis of Bou Denib. It’s been wiped out by a disease in Algeria and Morocco. We have sent back good plant stock to return to those areas from which they originated. My husband and I visited. It’s over the Atlas Mountains from Marrakech — out really in the desert. When we got to Bou Denib, the mayor came out to greet us. It was a big occasion. And he said why would anyone from the United States want to come to Bou Denib? We had worked with the Medjool dates for so many years and to see where they originated was very meaningful for us.