Per request.
According to Wiki:
The purpose of the XB-19 project was to test the flight characteristics and design techniques associated with giant bombers. Douglas Aircraft Company strongly wanted to cancel the project, because it was extremely expensive. Despite advances in technology that made the XB-19 obsolete before it was even completed, the Army Air Corps felt that the prototype would be useful for testing. Its construction took so long that competition for the contracts to make the XB-35 and XB-36 occurred two months before its first flight.
The plane finally flew on June 27, 1941, more than three years after the construction contract was awarded. In 1943, the original Wright R-3350 engines were replaced with Allison V-3420-11 V engines. After completion of testing, the XB-19 served as a cargo carrier until it was scrapped in 1949.The newly formed U.S. Air Force had begun plans to save the B-19 for eventual display, but in 1949 the Air Force did not yet have a program in place to save historic aircraft, and the Air Force Museum had not yet been constructed. As a result, the B-19 was scrapped, but two of its enormous main tires were saved. One was put on display at the Hill Aerospace Museum at Hill Air Force Base in Ogden, Utah and the other has been on display at the National Museum of the United States Air Force in Dayton, Ohio, in the "Early Years" gallery for many years.
Douglas XB-19 add

Douglas XB-19 under construction (US Air Force photo)

Douglas XB-19 under construction (US Air Force photo)

Douglas XB-19 under construction (US Air Force photo)

Douglas XB-19 tire (US Air Force photo)

Douglas XB-19 1941 (US Air Force photo)

XB-19 at March Field Calif on the day of its first flight June 27 1941

Douglas XB-19 (US Air Force photo)

Douglas XB-19 (US Air Force photo)

Douglas XB-19 (US Air Force photo)

Douglas XB-19 (US Air Force photo)

Douglas XB-19 (US Air Force photo)

Douglas XB-19 Hemisphere Defender cockpit

XB-19 November 1941 March Field California

XB-19 November 1941 March Field California

XB-19 wing inspection November 1941 March Field California

Douglas XB-19 in flight with camo finish (US Air Force photo)

Douglas XB-19 in flight with camo finish (US Air Force photo)

Douglas XB-19A (US Air Force photo)

Douglas XB-19A (US Air Force photo)

Douglas XB-19A (US Air Force photo)

Douglas XB-19A (US Air Force photo)

Douglas XB-19A nose section in the scrap pile (US Air Force photo)