USS Pittsburgh (SSN 720) is a Los Angeles-class attack submarine.
The Los Angeles-class, sometimes called the LA-class or the 688-class, is a class of nuclear-powered fast attack submarines that forms the backbone of the U.S. Navy's submarine force. Sixty-two submarines of this class have been completed, 41 are still in active service.
The Los Angeles class contains more nuclear submarines than any other class in the world. The class was preceded by the Sturgeon class and followed by the Seawolf. Except for USS Hyman G. Rickover (SSN 709), all submarines of this class are named after American cities and a few towns (e.g. Key West, Florida, and Greeneville, Tennessee). This system of naming broke the Navy’s long-standing tradition of naming attack submarines for creatures of the ocean (e.g. USS Nautilus (SSN 571).