Jacksonville is home to two major naval installations. Naval Air Station Jacksonville (NAS Jax), located on the St. Johns River, supports over 20,000 military and civilian employees and is one of the Navy's most important aviation logistics hubs. Naval Station Mayport on Jacksonville's Atlantic coast is the Navy's third-largest fleet concentration area, homeporting guided missile destroyers and amphibious assault ships. Together, these installations make Jacksonville one of the most military-saturated metro areas in the eastern United States.