I've noticed over the years that Palo Alto's residential areas started with a grid system but moved towards a cul-de-sac by blocking off roads to cut off parts

I've noticed over the years that Palo Alto's residential areas started with a grid system but moved towards a cul-de-sac by blocking off roads to cut off parts of the grid. The College Terrace area is particularly notable (likely because of its proximity to employment centers like Page Mill's corporate campuses and Stanford University), and I seem to recall the Old Palo Alto area having some road blocks as well (particularly the area directly south of Palo Alto High School). It definitely makes the quality of life better for the residents while making commuters "pay more" so to speak. I wonder when these road blocks (which are visually pleasing with trees and pedestrian and cyclist permeable) came to be.