The Strategic Petroleum Reserve is the world's largest supply of emergency crude oil. The reserve is maintained by the Department of Energy and is located along the coastline of the Gulf of Mexico in Louisiana and Texas in underground salt caverns. The Strategic Petroleum Reserve was started in 1975 after oil supplies were interrupted during the 1973–1974 oil embargo to mitigate future supply disruptions, providing a cushion against unexpected price spikes. It has a capacity of 727 million barrels, but as of September 6, 2019, the oil reserves totaled 644.8 million barrels. The maximum withdrawal capability is 4.4 million barrels per day, taking about 150 days to use the entire inventory.