The first purpose-built aircraft to fly the president of the United States, the Sacred Cow is the only VC-54C ever constructed.
Airplanes - Military - Static Display - Cargo
This VC-54C aircraft, nicknamed the Sacred Cow, included a sleeping area, radio telephone, and retractable elevator to lift Roosevelt in his wheelchair. The VC-54C was used by President Roosevelt only once before his death, on his trip to the Yalta Conference in February 1945.
The legislation that created the U.S. Air Force, the National Security Act of 1947, was signed by Truman while on board the VC-54C..
Links: en.wikipedia.org, www.nationalmuseum.af.mil