The Boxers were developed by a small group of German breeders during the very late 19th century. The breeds that make a Boxer are said to have been a mastiff called the Bullenbeiser (aka the "bull biter," which is now extinct) and a variety of Bulldogs from England. The Boxer was produced to be a faster hunting dog meant to bring down the same large game as its ancestors: bears, wild boar, etc.
The first club, the Deutscher Boxer Club, was responsible for the first Boxer breed standard. The standard had been first drafted in 1902 and faced fierce competition from competing Boxer breeders. Nevertheless, the American Kennel Club (AKC) adopted the Deutscher's breed standard the same year it was published in 1904.
During WWI, Boxers were used for a great many tasks by the German military. Had they been left behind in Europe after the war, Boxer history may well have ended there too. After the war, Ally soldiers took rescued Boxers home to the United States, where the breed's popularity grew quickly. The dog's first AKC Championship was taken in 1915, and in 1935 the American Boxer Club was established.