Finding locations of iPhone warehouses is a little difficult.
Apple stores iPhones in intermediate warehouses via UPS and FedEx. There is a warehouse facility in Elk Grove, California [18].
There is also a warehouse in Beijing, China. But, the only way I found out about this warehouse is through critically investigating the security of them.
Three men dug a tunnel into the Beijing warehouse and stole 240 iPhone 6’s. The total value was $228,496. The one guy knew where the building was because he was a driver for the logistics company that owned the building. The whole in the building was 50 centimeters in diameter. The men sold the iPhones and used it to purchase items, including cars. The police have caught the men and they tracked the stolen iPhones by their serial numbers [15].