Until the 1940's they never really were grown much in the United States. Benjamin Franklin was sent a sample of seeds and both he and Thomas Jefferson grew them. The coagulated protein is called tofu. Most of the U.S. soybean crop is consumed indirectly. Over half of our production is exported.
Soy beans are the most important bean crop in the world.
They go back perhaps 4000 years in Africa. They do well on poor soils. Black-eyed peas In a similar manner, Vigna unguiculata , was domesticated in Africa and brought to the Americas by black slaves. Other species of the genus are also widely cultivated in Asia. Romans and Greeks knew them.