It is well-known that proportional reasoning is one important hallmark of middle school mathematics. In this summer intensive workshop, Kara will help us to understand why proportionality matters and how we are developing these ideas in elementary mathematics. First, we will explore the development of multiplication and rational numbers (especially fractions) through investigations and guided number strings. Then, we will study the development of early algebra and algebraic reasoning, starting in grade 4. Finally, we will study how these overlapping landscapes provide the foundation for proportional reasoning.