<P> Western Europe and North America were the original major markets for large - scale lettuce production . By the late 1900s, Asia, South America, Australia and Africa became more substantial markets . Different locations tended to prefer different types of lettuce, with butterhead prevailing in northern Europe and Great Britain, romaine in the Mediterranean and stem lettuce in China and Egypt . By the late 20th century, the preferred types began to change, with crisphead, especially iceberg, lettuce becoming the dominant type in northern Europe and Great Britain and more popular in western Europe . In the US, no one type predominated until the early 20th century, when crisphead lettuces began gaining popularity . After the 1940s, with the development of iceberg lettuce, 95 percent of the lettuce grown and consumed in the US was crisphead lettuce . By the end of the century, other types began to regain popularity and eventually made up over 30 percent of production . Stem lettuce was first developed in China, and remains primarily cultivated in that country . </P> <P> In the early 21st century, bagged salad products increased in the lettuce market, especially in the US where innovative packaging and shipping methods prolonged freshness . </P> <P> In the United States in 2013, California (71%) and Arizona (29%) produced nearly all of the country's fresh head and leaf lettuce, with head lettuce yielding $9400 of value per acre and leaf lettuce $8000 per acre . </P> <P> As described around 50 AD, lettuce leaves were often cooked and served by the Romans with an oil - and - vinegar dressing; however, smaller leaves were sometimes eaten raw . During the 81--96 AD reign of Domitian, the tradition of serving a lettuce salad before a meal began . Post-Roman Europe continued the tradition of poaching lettuce, mainly with large romaine types, as well as the method of pouring a hot oil and vinegar mixture over the leaves . Today, the majority of lettuce is grown for its leaves, although one type is grown for its stem and one for its seeds, which are made into an oil . Most lettuce is used in salads, either alone or with other greens, vegetables, meats and cheeses . Romaine lettuce is often used for Caesar salads, with a dressing that includes anchovies and eggs . Lettuce leaves can also be found in soups, sandwiches and wraps, while the stems are eaten both raw and cooked . The consumption of lettuce in China developed differently from in Western countries, due to health risks and cultural aversion to eating raw leaves . In that country, "salads" were created from cooked vegetables and served hot or cold . Lettuce was also used in a larger variety of dishes than in Western countries, contributing to a range of dishes including bean curd and meat dishes, soups and stir - frys plain or with other vegetables . Stem lettuce, widely consumed in China, is eaten either raw or cooked, the latter primarily in soups and stir - frys . Lettuce is also used as a primary ingredient in the preparation of lettuce soup . </P>

Where is lettuce grown in the united states