The ACS-64, also known as the "Amtrak Cities Sprinter", is Amtraks replacement of the aging AEM-7 and HHP-8 electric locomotives for operation in the Northeast and Keystone Corridors. Built by Siemens and based on the Euro Sprinter European electric locomotive design, the Cities Sprinter is nonetheless a unique model to North America and is built entirely in the United States. #600 was the first of these locomotives to enter service and has special "David L. Gunn" Lettering on the nose to celebrate Amtraks president between 2002 and 2005.