Rottweilers accompanied the Roman Legions, herding their cattle and guarding their camps across the Alps. On the banks of the Neckar River in what is now southern Germany, was the origin of the town of Rottweil (named for the red tile roofs of the villas built by the Romans). The cattle trade flourished in Rottweil through the mid-1800s, as did the Rottweiler Metzgerhund (butcher dog), who drove the cattle to market and returned with the filled purses of their masters around their necks. As rail transportation became the primary means of bringing cattle to market, the dogs were used less frequently. By 1905, there was only one Rottweiler left in the town of Rottweil. The Rottweiler gained popularity as a police dog in the early 1900's. Several Clubs were formed, and in 1921 united as the Allgemeiner Deutscher Rottweiler Klub (ADRK). The first Rottweiler was admitted to the AKC Stud Book in 1931. The Rottweiler was a fairly uncommon dog in the United States through the 1970's, but the early 1980's began a meteoric rise in popularity. The Rottweiler is now the second most popular AKC breed since 1992.