The earliest written reference to Wagyu dates to about 1310 A.D
The Japanese Black was primarily used as the "workhorse" prior to the turn of the 20th Century. This breed was improved during the Meiji Era through crossbreeding with foreign breeds, and certified as indigigenous Japanese beef cattle in 1944. They were raised in most Prefectures of Japan, and more than 90% of Wagyu rasied and fattened in Japan is of this breed.
The breed called Wagyu (which means Japanese cow), became famous all over the world from the name "Kobe Beef". The Japanese government strictly regulates the breed, and only cattle produced in the Kobe region can be called "Kobe Beef". Elsewhere in the world you may see it labeled as "Kobe Style Beef" or Wagyu Beef, Only DNA verified Wagyu that are produced internationally can have the title of "Fullblood or 100% Wagyu cattle. Wagyu were originally draft animals used in agriculture, so they were chosen for physical endurance. This choosing favored animals with more intra-muscular fat cells, marbeling, which provided a naturally available energy source. Japanese Wagyu originate from native asian cattle, which were infused with British and European breeds in the late 1800's. Although the herd was closed to outside breed lines in 1910, isolation in the region produced a variety of different strains with varying conformations.
The first few fullblood sires were brought over between 1976 and 1997, and a handful of more important fullblood cattle were brought over to the U.S. in the 1990's until Japan deamed the Japanese Wagyu so important and valuable that they declared them a national treasure and are now protected. Less than 250 Wagyu were exported from Japan to the U.S., most of which were Japanese Black. Most Wagyu cattle herds in the U.S. are just a certain percentage Wagyu. Fullblood or 100% herds in the U.S. are small in comparison to that of Japan and Australia herds.