ABSTRACT
Introduction In the more than 150 years since early childhood education was introduced, and especially from 1960 onward, early childhood curricula and programs in the United States have assumed a wide variety in form and content. Variation in form and content has influenced the types of materials used, as well as the ways the classroom or early childhood center is furnished and arranged, the ways the day is scheduled, and the ways the world outside of the classroom is used to extend children's experience and learning.
