In the 1920’s, Clarence Perry introduced a concept that he referred to as “The Neighborhood Unit“.  The image below is a sketch published by Perry in 1929 illustrating the relationships between the residential components of a neighborhood and the uses that could easily be traversed to and from by foot.  Perry utilized the 5-minute walk (See The Five-Minute Walk: More Than Just a Circle for more information) to define walking distances from residential to non-residential components, in particular Perry was very concerned about the walkability to and from schools.
Full Story: The Neighborhood Unit: How Does Perry’s Concept Apply to Modern Day Planning? 

Clarence Perry's "Neighborhood Unit" Diagram, 1929.