What crops, sometimes called the "three sisters" were the first to be successfully grown by the mound builders in mississippi?

Winter squash, maize (corn), and climbing beans, are the right answers.

Explanation:

The main crops of many of the indigenous American groups are known as the Three Sisters. The three sisters included the winter squash, maize (corn), and climbing beans. The groups of Native Americans grew the Three Sister gardens throughout  North America. The Three Sisters is an example of a companion planting.