The Three Sisters – corn, beans, and squash – have been an important staple for Native American communities, both agriculturally and nutritionally, for centuries. By planting these three crops together, corn provides a support for beans to climb without competing with sprawling squash vines. In addition to their mutual growth benefits, a diet of corn, beans and squash is complete and balanced, with corn providing carbohydrates, beans protein, and squash minerals and vitamins. Although the Three Sisters have traditionally been grown in close proximity to one another, such as in the Haudenosaunee method, some communities choose to plant them separately to maximise limited water supply.
https://www.nativeseeds.org/blogs/blog-news/how-to-grow-a-three-sisters-garden