Pebble Dash was not Wright’s Idea (Part 2)

It was Arthur Richards, Wright's partner-developer from 1916-1917, who decided to cover the American System-Built Homes (ASBH) in Magnesite pebbles, not Frank Lloyd Wright. And where does one get Magnesite before 1917?

Why did Frank Lloyd Wright keep the drawings he planned to forget?

Why do the vintage American System Built Homes (ASBH) plans exist at all? Frank Lloyd Wright didn't plan to re-use or show them. Was his decision to store almost 1000 drawings based on nostalgia or pride, or something more practical?