When was the B1 bomber invented?

World War 1The Martin MB-1 or Glenn Martin Bomber was the first U.S.-designed bomber procured by the U.S. Army in quantity in the World War I era. The Martin GMB was first flown on Aug. 15, 1918, and nine of the 10 aircraft ordered were completed before the end of WWI.

Link with photo:

http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2414

Modern Stealth BomberThe B-1A Lancer bomber flew in 1974 . After several program cancellations, the a/c was re-designed to save costs and first production model of the revised B-1B first flew in October 1984. It became operational on October 1, 1986.