Lamb is the meat from a young sheep, up to about a year old, after which the meat becomes known as mutton. Mutton is a darker meat than lamb and has a slightly stronger flavor. It is rarely available in the United States.
Grasslands, both hillside and lowland, of temperate and cold climates, provide the right conditions for rearing sheep. These are widely distributed and so is lamb. It comes from the barren Asian steppes of Mongolia to the islands in the North Sea off the Netherlands where the famous Texel lamb is found; from the mountainsides of Colorado to lush grassy pastures of Kent and Sussex and those of the North Island of New Zealand where there is a far greater population of sheep than of humans. Human migration around the world helped to spread and develop sheep farming, both for wool and for food. The Welsh hill farmers took sheep with them to hilly Patagonia in South America. Basque shepherds from southwest France and northern Spain, said to be among the most skilled in the world, took sheep to the Pacific Northwest states of the United States, along with their spices and methods of cooking.