where was deepwater horizon

Deepwater Horizon was an offshore drilling rig in the Gulf of Mexico, positioned on the Macondo Prospect in the U.S. sector, about 41 miles off the Louisiana coast.

Quick answer

It was not on land or in a city; it was a floating drilling platform at sea.

More specific location

• Gulf of Mexico
• Macondo Prospect / Mississippi Canyon Block 252
• About 41 miles (66 km) off Louisiana

If you want, I can also show you a simple map-style description of where that is.