US Military Sealift Command Large Medium Speed Ro Ro Vehicle Cargo Ship of the Gordon Class (2nd of 2).
Originally built in 1972 as the M/V Selandia, converted and put into service 1997.
When not in use, she is maintained in Ready Operation Status 4 (can be activated in 4 days) in the MSC Atlantic Surge Force.
She can carry an entire US Army Heavy Battalion Size Task Force of Main Battle Tanks and other vehicles or the equivalent.
Seen here going west past Fort Monroe Hampton VA towards Newport News VA. There is a dock near the Monitor Merrimac Bridge Tunnel System there where a number of MSC/RRF Ro-Ro Ships are docked Mediterranean Style.

http://www.navsource.org/archives/09/54/540298.htm
https://www.navysite.de/akr/akr298.htm