Romaine is the American term for this long leafed lettuce, also called cos or cos lettuce because it is said to have originated on the Greek island of Cos (Kos), off the coast of Turkey in the Aegean Sea.  Other known names are Roman and Manchester.

Egyptian tombs reveal paintings of lettuce with long, pointed leaves, resembling romaine. It was known to the Romans, who usually ate lettuce cooked, as Cappadocian lettuce, and was called Roman lettuce due to the Romans belief in its healthful and healing properties. The emperor Augustus Caesar is said to have put up a statue to honor its healing abilities after being cured of a serious illness. A white latex oozes from its leaf base and the thicker ribs of older, larger leaves and is reflected in the first syllable of its Latin name, Lactuca, which means milk. Lettuce juice was used as a medicine by many ancient herbalists.

Romaine is a member of the daisy family, Compositae, which is the second largest family of flowering plants. 

Romaine is the most nutritious of all lettuces and is an excellent source of vitamin C (5 times more than iceberg lettuce).   

In China, where lettuce has been growing since the 5th century, lettuce represents good luck. It is served on birthdays, New Year's Day and other special occasions.

Christopher Columbus introduced varieties of lettuce to North America during his second voyage in 1493. Lettuce was first planted in California, the lettuce capital of the United States, by the Spanish missionaries in the 17th century. Its popularity across the US did not become widespread until centuries later with the development of refrigeration and railway transportation.