Amaranth
Amaranth, a member of the amaranth family, can be used alone as a flour substitute or mixed with other grains. Amaranth was used by the Aztecs some 3,000 years ago, and was their primary source of food. In order to control the Aztec population, Cortez ordered all the amaranth destroyed.
It was recently rediscovered growing wild in Central America, and was brought back to the United States. Since it is still a relatively new crop, only a small amount is grown in America at present. It is high in protein, and is especially good for those who must restrict grains and dairy foods. When mixed with grain or a food containing thiamine (i.e. pork), it contains 100% of the essential amino acids.
References
Yoder, Eileen. Allergy-Free Cooking. Addison-Wesley Publ Co., Reading, MA, 1987.