2,050 citizen soldiers and airmen have been activated by state governors, and that number will likely double by the weekend.
The Defense Production Act of 1950 was signed by President Truman amid concerns about supplies and equipment during that war.
President Trump said Wednesday that the Navy's pair of hospital ships will soon be stationed on the East and West coasts.
The U.S. has seen a shortage of testing kits as the novel coronavirus, or COVID-19, spreads.
Officials caution the hospitals are designed to treat combat trauma, not infectious diseases.
But the defense secretary urged caution on the deployment of field hospitals and the Army Corps of Engineers.
New Rochelle and surrounding Westchester County account for at least 108 cases out of 173 statewide.
The Pentagon stressed that the locations have been named as precautionary backup locations.
Camp Ashland, a Nebraska National Guard base roughly 30 miles from Omaha, will house the latest evacuees.
Two jetliners carrying 350 American evacuees from the epicenter of China's coronavirus outbreak landed Wednesday at Travis.