Johnson - not to be confused with the modernist architect, was quite a connected character. He designed many firehouses, etc. He "landed a lifetime contract with the City Health Department that earned his office more than $2 million in fees over three decades." More here.
From where you started, I was hoping to hear more about the design typologies, the Cottage Plan, etc.
Thank you as always for your thoughtful comments, and for your additional information on Johnson!
I had originally hoped to focus on Pennhurst's architecture but had a change of mind midway through. Now, however, I am thinking I may write a related post in the future along the lines you suggest. I would be interested to see the chronology and philosophies behind plans like the Cottage Plan (and its successive iterations), the Kirkbride Plan, and so forth. Thanks again!