TI list member Bruce Hettema is the owner of P&H Creative Group and the author of an article in the current issue of Illustration magazine on the history of his Petaluma, California art studio, which began life in the 1920's in San Francisco as Patterson & Sullivan.
The studio's key artist at this time was W. Haines Hall, who had joined the firm in 1925 and continued to be active in the business through the 1960's.
Haines, along with fellow employee Alton Painter, was a founding member of the Thirteen watercolorists (founded by Maynard Dixon and Maurice Logan). He was also active in the Bohemian Club, producing posters and portraits for their various events.
Seavey's cartoons of the P&S artists often portrayed Haines as the sage arbiter amidst the turmoil and pandemonium of a bustling art studio.
So, after Sullivan left the business in 1939 (or more accurately "the business left him", Hall was J.E.'s first choice to become his new partner.
This quite naturally led to a name change: Patterson & Sullivan became Patterson & Hall.
You can find the full length version of this article in Illustration magazine #19.